Sledding A sled with a mass of 50.0 kg is pulled along

Chapter 5: Problem 1 Physics: Principles & Problems 9

A car is driven 125.0 km due west, then 65.0 km due south. What is the magnitude of its displacement? Solve this problem both graphically and mathematically, and check your answers against each other

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Chapter 5: Problem 2 Physics: Principles & Problems 9

Two shoppers walk from the door of the mall to their car, which is 250.0 m down a lane of cars, and then turn 90 to the right and walk an additional 60.0 m. What is the magnitude of the displacement of the shoppers car from the mall door? Solve this problem both graphically and mathematically, and check your answers against each other

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Chapter 5: Problem 3 Physics: Principles & Problems 9

A hiker walks 4.5 km in one direction, then makes a 45 turn to the right and walks another 6.4 km. What is the magnitude of her displacement?

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Chapter 5: Problem 4 Physics: Principles & Problems 9

An ant is crawling on the sidewalk. At one moment, it is moving south a distance of 5.0 mm. It then turns southwest and crawls 4.0 mm. What is the magnitude of the ants displacement?

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Chapter 5: Problem 5 Physics: Principles & Problems 9

Sudhir walks 0.40 km in a direction 60.0 west of north, then goes 0.50 km due west. What is his displacement?

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Chapter 5: Problem 6 Physics: Principles & Problems 9

Afua and Chrissy are going to sleep overnight in their tree house and are using some ropes to pull up a box containing their pillows and blankets, which have a total mass of 3.20 kg. The girls stand on different branches, as shown in Figure 5-6, and pull at the angles and with the forces indicated. Find the x- and y-components of the net force on the box. Hint: Draw a free-body diagram so that you do not leave out a force

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Chapter 5: Problem 7 Physics: Principles & Problems 9

You first walk 8.0 km north from home, then walk east until your displacement from home is 10.0 km. How far east did you walk?

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Chapter 5: Problem 8 Physics: Principles & Problems 9

A childs swing is held up by two ropes tied to a tree branch that hangs 13.0 from the vertical. If the tension in each rope is 2.28 N, what is the combined force (magnitude and direction) of the two ropes on the swing?

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Chapter 5: Problem 9 Physics: Principles & Problems 9

Could a vector ever be shorter than one of its components? Equal in length to one of its components? Explain.

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Chapter 5: Problem 10 Physics: Principles & Problems 9

In a coordinate system in which the x-axis is east, for what range of angles is the x-component positive? For what range is it negative?

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Chapter 5: Problem 11 Physics: Principles & Problems 9

Distance v. Displacement Is the distance that you walk equal to the magnitude of your displacement? Give an example that supports your conclusion.

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Chapter 5: Problem 12 Physics: Principles & Problems 9

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Chapter 5: Problem 13 Physics: Principles & Problems 9

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Chapter 5: Problem 14 Physics: Principles & Problems 9

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Chapter 5: Problem 15 Physics: Principles & Problems 9

Commutative Operations The order in which vectors are added does not matter. Mathematicians say that vector addition is commutative. Which ordinary arithmetic operations are commutative? Which are not?

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Chapter 5: Problem 16 Physics: Principles & Problems 9

Critical Thinking A box is moved through one displacement and then through a second displacement. The magnitudes of the two displacements are unequal. Could the displacements have directions such that the resultant displacement is zero? Suppose the box was moved through three displacements of unequal magnitude. Could the resultant displacement be zero? Support your conclusion with a diagram.

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Chapter 5: Problem 17 Physics: Principles & Problems 9

A girl exerts a 36-N horizontal force as she pulls a 52-N sled across a cement sidewalk at constant speed. What is the coefficient of kinetic friction between the sidewalk and the metal sled runners? Ignore air resistance.

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Chapter 5: Problem 18 Physics: Principles & Problems 9

You need to move a 105-kg sofa to a different location in the room. It takes a force of 102 N to start it moving. What is the coefficient of static friction between the sofa and the carpet?

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Chapter 5: Problem 19 Physics: Principles & Problems 9

Mr. Ames is dragging a box full of books from his office to his car. The box and books together have a combined weight of 134 N. If the coefficient of static friction between the pavement and the box is 0.55, how hard must Mr. Ames push the box in order to start it moving?

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Chapter 5: Problem 20 Physics: Principles & Problems 9

Suppose that the sled in problem 17 is resting on packed snow. The coefficient of kinetic friction is now only 0.12. If a person weighing 650 N sits on the sled, what force is needed to pull the sled across the snow at constant speed?

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Chapter 5: Problem 21 Physics: Principles & Problems 9

Suppose that a particular machine in a factory has two steel pieces that must rub against each other at a constant speed. Before either piece of steel has been treated to reduce friction, the force necessary to get them to perform properly is 5.8 N. After the pieces have been treated with oil, what will be the required force?

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Chapter 5: Problem 22 Physics: Principles & Problems 9

A 1.4-kg block slides across a rough surface such that it slows down with an acceleration of 1.25 m/s2. What is the coefficient of kinetic friction between the block and the surface?

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Chapter 5: Problem 23 Physics: Principles & Problems 9

You help your mom move a 41-kg bookcase to a different place in the living room. If you push with a force of 65 N and the bookcase accelerates at 0.12 m/s2, what is the coefficient of kinetic friction between the bookcase and the carpet?

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Chapter 5: Problem 24 Physics: Principles & Problems 9

A shuffleboard disk is accelerated to a speed of 5.8 m/s and released. If the coefficient of kinetic friction between the disk and the concrete court is 0.31, how far does the disk go before it comes to a stop? The courts are 15.8 m long

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Chapter 5: Problem 25 Physics: Principles & Problems 9

Consider the force pushing the box in Example Problem 4. How long would it take for the velocity of the box to double to 2.0 m/s?

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Chapter 5: Problem 26 Physics: Principles & Problems 9

Ke Min is driving along on a rainy night at 23 m/s when he sees a tree branch lying across the road and slams on the brakes when the branch is 60.0 m in front of him. If the coefficient of kinetic friction between the cars locked tires and the road is 0.41, will the car stop before hitting the branch? The car has a mass of 2400 kg.

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Chapter 5: Problem 27 Physics: Principles & Problems 9

Friction In this section, you learned about static and kinetic friction. How are these two types of friction similar? What are the differences between static and kinetic friction?

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Chapter 5: Problem 28 Physics: Principles & Problems 9

Friction At a wedding reception, you notice a small boy who looks like his mass is about 25 kg running part way across the dance floor, then sliding on his knees until he stops. If the kinetic coefficient of friction between the boys pants and the floor is 0.15, what is the frictional force acting on him as he slides?

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Chapter 5: Problem 29 Physics: Principles & Problems 9

Velocity Derek is playing cards with his friends, and it is his turn to deal. A card has a mass of 2.3 g, and it slides 0.35 m along the table before it stops. If the coefficient of kinetic friction between the card and the table is 0.24, what was the initial speed of the card as it left Dereks hand?

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Chapter 5: Problem 30 Physics: Principles & Problems 9

Force The coefficient of static friction between a 40.0-kg picnic table and the ground below it is 0.43. What is the greatest horizontal force that could be exerted on the table while it remains stationary?

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Chapter 5: Problem 31 Physics: Principles & Problems 9

Acceleration Ryan is moving to a new apartment and puts a dresser in the back of his pickup truck. When the truck accelerates forward, what force accelerates the dresser? Under what circumstances could the dresser slide? In which direction?

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Chapter 5: Problem 32 Physics: Principles & Problems 9

Critical Thinking You push a 13-kg table in the cafeteria with a horizontal force of 20 N, but it does not move. You then push it with a horizontal force of 25 N, and it accelerates at 0.26 m/s2. What, if anything, can you conclude about the coefficients of static and kinetic friction?

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Chapter 5: Problem 33 Physics: Principles & Problems 9

An ant climbs at a steady speed up the side of its anthill, which is inclined 30.0 from the vertical. Sketch a free-body diagram for the ant.

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Chapter 5: Problem 34 Physics: Principles & Problems 9

Scott and Becca are moving a folding table out of the sunlight. A cup of lemonade, with a mass of 0.44 kg, is on the table. Scott lifts his end of the table before Becca does, and as a result, the table makes an angle of 15.0 with the horizontal. Find the components of the cups weight that are parallel and perpendicular to the plane of the table.

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Chapter 5: Problem 35 Physics: Principles & Problems 9

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Chapter 5: Problem 36 Physics: Principles & Problems 9

Fernando, who has a mass of 43.0 kg, slides down the banister at his grandparents house. If the banister makes an angle of 35.0 with the horizontal, what is the normal force between Fernando and the banister?

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Chapter 5: Problem 37 Physics: Principles & Problems 9

A suitcase is on an inclined plane. At what angle, relative to the vertical, will the component of the suitcases weight parallel to the plane be equal to half the perpendicular component of its weight?

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Chapter 5: Problem 38 Physics: Principles & Problems 9

Consider the crate on the incline in Example Problem 5. Calculate the magnitude of the acceleration. After 4.00 s, how fast will the crate be moving?

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Chapter 5: Problem 39 Physics: Principles & Problems 9

If the skier in Example Problem 6 were on a 31 downhill slope, what would be the magnitude of the acceleration?

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Chapter 5: Problem 40 Physics: Principles & Problems 9

Stacie, who has a mass of 45 kg, starts down a slide that is inclined at an angle of 45 with the horizontal. If the coefficient of kinetic friction between Stacies shorts and the slide is 0.25, what is her acceleration?

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Chapter 5: Problem 41 Physics: Principles & Problems 9

After the skier on the 37 hill in Example Problem 6 had been moving for 5.0 s, the friction of the snow suddenly increased and made the net force on the skier zero. What is the new coefficient of friction?

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Chapter 5: Problem 42 Physics: Principles & Problems 9

Forces One way to get a car unstuck is to tie one end of a strong rope to the car and the other end to a tree, then push the rope at its midpoint at right angles to the rope. Draw a free-body diagram and explain why even a small force on the rope can exert a large force on the car

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Chapter 5: Problem 43 Physics: Principles & Problems 9

Mass A large scoreboard is suspended from the ceiling of a sports arena by 10 strong cables. Six of the cables make an angle of 8.0 with the vertical while the other four make an angle of 10.0. If the tension in each cable is 1300.0 N, what is the scoreboards mass?

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Chapter 5: Problem 44 Physics: Principles & Problems 9

Acceleration A 63-kg water skier is pulled up a 14.0 incline by a rope parallel to the incline with a tension of 512 N. The coefficient of kinetic friction is 0.27. What are the magnitude and direction of the skiers acceleration?

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Chapter 5: Problem 45 Physics: Principles & Problems 9

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Chapter 5: Problem 46 Physics: Principles & Problems 9

Critical Thinking Can the coefficient of friction ever have a value such that a skier would be able to slide uphill at a constant velocity? Explain why or why not. Assume there are no other forces acting on the skier.

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Chapter 5: Problem 47 Physics: Principles & Problems 9

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Chapter 5: Problem 48 Physics: Principles & Problems 9

How would you add two vectors graphically?

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Chapter 5: Problem 49 Physics: Principles & Problems 9

. Which of the following actions is permissible when you graphically add one vector to another: moving the vector, rotating the vector, or changing the vectors length?

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Chapter 5: Problem 50 Physics: Principles & Problems 9

In your own words, write a clear definition of the resultant of two or more vectors. Do not explain how to find it; explain what it represents

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Chapter 5: Problem 51 Physics: Principles & Problems 9

How is the resultant displacement affected when two displacement vectors are added in a different order?

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Chapter 5: Problem 52 Physics: Principles & Problems 9

Explain the method that you would use to subtract two vectors graphically

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Chapter 5: Problem 53 Physics: Principles & Problems 9

. Explain the difference between A and A

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Chapter 5: Problem 54 Physics: Principles & Problems 9

The Pythagorean theorem usually is written c2 ! a2 " b2. If this relationship is used in vector addition, what do a, b, and c represent?

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Chapter 5: Problem 55 Physics: Principles & Problems 9

When using a coordinate system, how is the angle or direction of a vector determined with respect to the axes of the coordinate system?

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Chapter 5: Problem 56 Physics: Principles & Problems 9

. What is the meaning of a coefficient of friction that is greater than 1.0? How would you measure it?

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Chapter 5: Problem 57 Physics: Principles & Problems 9

Cars Using the model of friction described in this textbook, would the friction between a tire and the road be increased by a wide rather than a narrow tire? Explain

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Chapter 5: Problem 58 Physics: Principles & Problems 9

Describe a coordinate system that would be suitable for dealing with a problem in which a ball is thrown up into the air.

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Chapter 5: Problem 59 Physics: Principles & Problems 9

If a coordinate system is set up such that the positive x-axis points in a direction 30 above the horizontal, what should be the angle between the x-axis and the y-axis? What should be the direction of the positive y-axis?

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Chapter 5: Problem 60 Physics: Principles & Problems 9

. Explain how you would set up a coordinate system for motion on a hill.

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Chapter 5: Problem 61 Physics: Principles & Problems 9

If your textbook is in equilibrium, what can you say about the forces acting on it?

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Chapter 5: Problem 62 Physics: Principles & Problems 9

Can an object that is in equilibrium be moving? Explain

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Chapter 5: Problem 63 Physics: Principles & Problems 9

What is the sum of three vectors that, when placed tip to tail, form a triangle? If these vectors represent forces on an object, what does this imply about the object?

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Chapter 5: Problem 64 Physics: Principles & Problems 9

You are asked to analyze the motion of a book placed on a sloping table. (5.3) a. Describe the best coordinate system for analyzing the motion. b. How are the components of the weight of the book related to the angle of the table?

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Chapter 5: Problem 65 Physics: Principles & Problems 9

For a book on a sloping table, describe what happens to the component of the weight force parallel to the table and the force of friction on the book as you increase the angle that the table makes with the horizontal. (5.3) a. Which components of force(s) increase when the angle increases? b. Which components of force(s) decrease?

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Chapter 5: Problem 66 Physics: Principles & Problems 9

A vector that is 1 cm long represents a displacement of 5 km. How many kilometers are represented by a 3-cm vector drawn to the same scale?

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Chapter 5: Problem 67 Physics: Principles & Problems 9

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Chapter 5: Problem 68 Physics: Principles & Problems 9

A vector drawn 15 mm long represents a velocity of 30 m/s. How long should you draw a vector to represent a velocity of 20 m/s?

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Chapter 5: Problem 69 Physics: Principles & Problems 9

What is the largest possible displacement resulting from two displacements with magnitudes 3 m and 4 m? What is the smallest possible resultant? Draw sketches to demonstrate your answers.

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Chapter 5: Problem 70 Physics: Principles & Problems 9

How does the resultant displacement change as the angle between two vectors increases from 0 to 180?

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Chapter 5: Problem 71 Physics: Principles & Problems 9

A and B are two sides of a right triangle, where tan ! " A/B. a. Which side of the triangle is longer if tan ! is greater than 1.0? b. Which side is longer if tan ! is less than 1.0? c. What does it mean if tan ! is equal to 1.0?

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Chapter 5: Problem 72 Physics: Principles & Problems 9

Traveling by Car A car has a velocity of 50 km/h in a direction 60 north of east. A coordinate system with the positive x-axis pointing east and a positive y-axis pointing north is chosen. Which component of the velocity vector is larger, x or y?

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Chapter 5: Problem 73 Physics: Principles & Problems 9

. Under what conditions can the Pythagorean theorem, rather than the law of cosines, be used to find the magnitude of a resultant vector?

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Chapter 5: Problem 74 Physics: Principles & Problems 9

A problem involves a car moving up a hill, so a coordinate system is chosen with the positive x-axis parallel to the surface of the hill. The problem also involves a stone that is dropped onto the car. Sketch the problem and show the components of the velocity vector of the stone

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Chapter 5: Problem 75 Physics: Principles & Problems 9

Pulling a Cart According to legend, a horse learned Newtons laws. When the horse was told to pull a cart, it refused, saying that if it pulled the cart forward, according to Newtons third law, there would be an equal force backwards; thus, there would be balanced forces, and, according to Newtons second law, the cart would not accelerate. How would you reason with this horse?

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Chapter 5: Problem 76 Physics: Principles & Problems 9

Tennis When stretching a tennis net between two posts, it is relatively easy to pull one end of the net hard enough to remove most of the slack, but you need a winch to take the last bit of slack out of the net to make the top almost completely horizontal. Why is this true?

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Chapter 5: Problem 77 Physics: Principles & Problems 9

. The weight of a book on an inclined plane can be resolved into two vector components, one along the plane, and the other perpendicular to it. a. At what angle are the components equal? b. At what angle is the parallel component equal to zero? c. At what angle is the parallel component equal to the weight?

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Chapter 5: Problem 78 Physics: Principles & Problems 9

TV Towers The transmitting tower of a TV station is held upright by guy wires that extend from the top of the tower to the ground. The force along the guy wires can be resolved into two perpendicular components. Which one is larger?

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Chapter 5: Problem 79 Physics: Principles & Problems 9

Cars A car moves 65 km due east, then 45 km due west. What is its total displacement?

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Chapter 5: Problem 80 Physics: Principles & Problems 9

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Chapter 5: Problem 81 Physics: Principles & Problems 9

Graphically find the sum of the following pairs of vectors, whose lengths and directions are shown in Figure 5-17. a. D and A b. C and D c. C and A d. E and F

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Chapter 5: Problem 82 Physics: Principles & Problems 9

Graphically add the following sets of vectors, as shown in Figure 5-17. a. A, C, and D b. A, B, and E c. B, D, and F

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Chapter 5: Problem 83 Physics: Principles & Problems 9

You walk 30 m south and 30 m east. Find the magnitude and direction of the resultant displacement both graphically and algebraically.

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Chapter 5: Problem 84 Physics: Principles & Problems 9

Hiking A hikers trip consists of three segments. Path A is 8.0 km long heading 60.0 north of east. Path B is 7.0 km long in a direction due east. Path C is 4.0 km long heading 315 counterclockwise from east. a. Graphically add the hikers displacements in the order A, B, C. b. Graphically add the hikers displacements in the order C, B, A. c. What can you conclude about the resulting displacements

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Chapter 5: Problem 85 Physics: Principles & Problems 9

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Chapter 5: Problem 86 Physics: Principles & Problems 9

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Chapter 5: Problem 87 Physics: Principles & Problems 9

A Ship at Sea A ship at sea is due into a port 500.0 km due south in two days. However, a severe storm comes in and blows it 100.0 km due east from its original position. How far is the ship from its destination? In what direction must it travel to reach its destination?

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Chapter 5: Problem 88 Physics: Principles & Problems 9

Space Exploration A descent vehicle landing on Mars has a vertical velocity toward the surface of Mars of 5.5 m/s. At the same time, it has a horizontal velocity of 3.5 m/s. a. At what speed does the vehicle move along its descent path? b. At what angle with the vertical is this path?

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Chapter 5: Problem 89 Physics: Principles & Problems 9

Navigation Alfredo leaves camp and, using a compass, walks 4 km E, then 6 km S, 3 km E, 5 km N, 10 km W, 8 km N, and, finally, 3 km S. At the end of three days, he is lost. By drawing a diagram, compute how far Alfredo is from camp and which direction he should take to get back to camp.

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Chapter 5: Problem 90 Physics: Principles & Problems 9

If you use a horizontal force of 30.0 N to slide a 12.0-kg wooden crate across a floor at a constant velocity, what is the coefficient of kinetic friction between the crate and the floor?

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Chapter 5: Problem 91 Physics: Principles & Problems 9

A 225-kg crate is pushed horizontally with a force of 710 N. If the coefficient of friction is 0.20, calculate the acceleration of the crate

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Chapter 5: Problem 92 Physics: Principles & Problems 9

. A force of 40.0 N accelerates a 5.0-kg block at 6.0 m/s2 along a horizontal surface. a. How large is the frictional force? b. What is the coefficient of friction?

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Chapter 5: Problem 93 Physics: Principles & Problems 9

Moving Appliances Your family just had a new refrigerator delivered. The delivery man has left and you realize that the refrigerator is not quite in the right position, so you plan to move it several centimeters. If the refrigerator has a mass of 180 kg, the coefficient of kinetic friction between the bottom of the refrigerator and the floor is 0.13, and the static coefficient of friction between these same surfaces is 0.21, how hard do you have to push horizontally to get the refrigerator to start moving?

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Chapter 5: Problem 94 Physics: Principles & Problems 9

Stopping at a Red Light You are driving a 2500.0-kg car at a constant speed of 14.0 m/s along a wet, but straight, level road. As you approach an intersection, the traffic light turns red. You slam on the brakes. The cars wheels lock, the tires begin skidding, and the car slides to a halt in a distance of 25.0 m. What is the coefficient of kinetic friction between your tires and the wet road?

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Chapter 5: Problem 95 Physics: Principles & Problems 9

. An object in equilibrium has three forces exerted on it. A 33.0-N force acts at 90.0 from the x-axis and a 44.0-N force acts at 60.0 from the x-axis. What are the magnitude and direction of the third force?

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Chapter 5: Problem 96 Physics: Principles & Problems 9

Five forces act on an object: (1) 60.0 N at 90.0, (2) 40.0 N at 0.0, (3) 80.0 N at 270.0, (4) 40.0 N at 180.0, and (5) 50.0 N at 60.0. What are the magnitude and direction of a sixth force that would produce equilibrium?

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Chapter 5: Problem 97 Physics: Principles & Problems 9

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Chapter 5: Problem 98 Physics: Principles & Problems 9

A street lamp weighs 150 N. It is supported by two wires that form an angle of 120.0 with each other. The tensions in the wires are equal. a. What is the tension in each wire supporting the street lamp? b. If the angle between the wires supporting the street lamp is reduced to 90.0, what is the tension in each wire?

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Chapter 5: Problem 99 Physics: Principles & Problems 9

A 215-N box is placed on an inclined plane that makes a 35.0 angle with the horizontal. Find the component of the weight force parallel to the planes surface

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Chapter 5: Problem 100 Physics: Principles & Problems 9

Emergency Room You are shadowing a nurse in the emergency room of a local hospital. An orderly wheels in a patient who has been in a very serious accident and has had severe bleeding. The nurse quickly explains to you that in a case like this, the patients bed will be tilted with the head downward to make sure the brain gets enough blood. She tells you that, for most patients, the largest angle that the bed can be tilted without the patient beginning to slide off is 32.0 from the horizontal. a. On what factor or factors does this angle of tilting depend? b. Find the coefficient of static friction between a typical patient and the beds sheets.

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Chapter 5: Problem 101 Physics: Principles & Problems 9

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Chapter 5: Problem 102 Physics: Principles & Problems 9

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Chapter 5: Problem 103 Physics: Principles & Problems 9

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Chapter 5: Problem 104 Physics: Principles & Problems 9

Sledding A sled with a mass of 50.0 kg is pulled along flat, snow-covered ground. The static friction coefficient is 0.30, and the kinetic friction coefficient is 0.10. a. What does the sled weigh? b. What force will be needed to start the sled moving? c. What force is needed to keep the sled moving at a constant velocity? d. Once moving, what total force must be applied to the sled to accelerate it at 3.0 m/s2?

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Chapter 5: Problem 105 Physics: Principles & Problems 9

Mythology Sisyphus was a character in Greek mythology who was doomed in Hades to push a boulder to the top of a steep mountain. When he reached the top, the boulder would slide back down the mountain and he would have to start all over again. Assume that Sisyphus slides the boulder up the mountain without being able to roll it, even though in most versions of the myth, he rolled it. a. If the coefficient of kinetic friction between the boulder and the mountainside is 0.40, the mass of the boulder is 20.0 kg, and the slope of the mountain is a constant 30.0, what is the force that Sisyphus must exert on the boulder to move it up the mountain at a constant velocity? b. If Sisyphus pushes the boulder at a velocity of 0.25 m/s and it takes him 8.0 h to reach the top of the mountain, what is the mythical mountains vertical height?

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Chapter 5: Problem 106 Physics: Principles & Problems 9

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Chapter 5: Problem 107 Physics: Principles & Problems 9

Use Models Using the Example Problems in this chapter as models, write an example problem to solve the following problem. Include the following sections: Analyze and Sketch the Problem, Solve for the Unknown (with a complete strategy), and Evaluate the Answer. A driver of a 975-kg car traveling 25 m/s puts on the brakes. What is the shortest distance it will take for the car to stop? Assume that the road is concrete, the force of friction of the road on the tires is constant, and the tires do not slip.

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Chapter 5: Problem 108 Physics: Principles & Problems 9

Analyze and Conclude Margaret Mary, Doug, and Kako are at a local amusement park and see an attraction called the Giant Slide, which is simply a very long and high inclined plane. Visitors at the amusement park climb a long flight of steps to the top of the 27 inclined plane and are given canvas sacks. They sit on the sacks and slide down the 70- m-long plane. At the time when the three friends walk past the slide, a 135-kg man and a 20-kg boy are each at the top preparing to slide down. I wonder how much less time it will take the man to slide down than it will take the boy, says Margaret Mary. I think the boy will take less time, says Doug. Youre both wrong, says Kako. They will reach the bottom at the same time. a. Perform the appropriate analysis to determine who is correct. b. If the man and the boy do not take the same amount of time to reach the bottom of the slide, calculate how many seconds of difference there will be between the two times.

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Chapter 5: Problem 109 Physics: Principles & Problems 9

Investigate some of the techniques used in industry to reduce the friction between various parts of machines. Describe two or three of these techniques and explain the physics of how they work.

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Chapter 5: Problem 110 Physics: Principles & Problems 9

Olympics In recent years, many Olympic athletes, such as sprinters, swimmers, skiers, and speed skaters, have used modified equipment to reduce the effects of friction and air or water drag. Research a piece of equipment used by one of these types of athletes and the way it has changed over the years. Explain how physics has impacted these changes

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Chapter 5: Problem 111 Physics: Principles & Problems 9

. Add or subtract as indicated and state the answer with the correct number of significant digits. (Chapter 1) a. 85.26 g ! 4.7 g b. 1.07 km ! 0.608 km c. 186.4 kg " 57.83 kg d. 60.08 s " 12.2 s

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Chapter 5: Problem 112 Physics: Principles & Problems 9

You ride your bike for 1.5 h at an average velocity of 10 km/h, then for 30 min at 15 km/h. What is your average velocity? (Chapter 3)

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Chapter 5: Problem 113 Physics: Principles & Problems 9

A 45-N force is exerted in the upward direction on a 2.0-kg briefcase. What is the acceleration of the briefcase? (

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