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# Exam 2 PHYS 211

Penn State

GPA 3.9

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This 7 page Bundle was uploaded by Aaditya Solanki on Monday March 7, 2016. The Bundle belongs to PHYS 211 at Portland State University taught by Dr. ub dula in Spring 2016. Since its upload, it has received 129 views. For similar materials see Mechanics in Physics 2 at Portland State University.

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Date Created: 03/07/16

Exam Name___________________________________ MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A ball is tossed vertically upward. When it reaches its highest point (before falling back 1) downward) A) the velocity, acceleration, and the force of gravity on the ball all reverse direction. B) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is directed downward. C) the velocity and acceleration reverse direction, but the force of gravity on the ball remains downward. D) the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward. E) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is zero. 2) A dog is standing in the bed of a pickup truck. The bed is coated with ice, causing the force of 2) friction between the dog and the truck to be zero. The truck is initially at rest, and then accelerates to the right, moving along a ﬂat road. As seen from a stationary observer (watching the truck move to the right), the dog A) moves to the right, but not as quickly as the truck is moving to the right, causing it to slide towards the back of the truck. B) does not move left or right, but the back of the truck moves towards the dog. C) moves to the left, as the truck moves to the right, causing the dog to slide towards the back of the truck. D) moves to the right at the same rate as the truck, so it doesn't slide. 3) A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. 3) Which of the following forces is the other force if the acceleration of the object is 1.0 m/s toward the east? A) 7.0 N west B) 9.0 N west C) 3.0 N west D) 6.0 N east E) 12 N east 4) An 1100-kg car traveling at 27.0 m/s starts to slow down and comes to a complete stop in 578 m. 4) What is the magnitude of the average braking force acting on the car? A) 410 N B) 550 N C) 340 N D) 690 N 2 5) On its own, a certain tow-truck has a maximum acceleration of 3.0 m/s . What would be the 5) maximum acceleration when this truck was towing a bus of twice its own mass? 2 2 2 2 A) 1.5 m/s B) 2.5 m/s C) 2.0 m/s D) 1.0 m/s 1 6) An object weighing 4.00 N falls from rest subject to a frictional drag force given bydrag =bv ,2 6) where v is the speed of the object andb = 3.00N∙ s /m . What terminal speed will this object approach? A) 2.25 m/s B) 3.42 m/s C) 1.15 m/s D) 1.78 m/s E) 0.75 m/s 7) Two forces act on a55-kg object. One force has magnitude 65 N directed 59° clockwise from the 7) positivex-axis, and the other has a magnitude 35 N at 32° clockwise from the positive y-axis. What is the magnitude of this object's acceleration? 2 2 2 2 A) 1.1 m/s B) 1.3 m/s C) 1.7 m/s D) 1.5 m/s 8) A ﬁsh weighing 16 N is weighed using two spring scales, each of negligible weight, as shown in 8) the ﬁgure. What will be the readings of the scales? A) Each scale will read 16 N. B) The scales will have different readings, but the sum of the two readings will be 16 N. C) The top scale will read 16 N, and the bottom scale will read zero. D) Each scale will read 8 N. E) The bottom scale will read 16 N, and the top scale will read zero. 9) Two objects have massesm and 5m, respectively. They both are placed side by side on a 9) frictionless inclined plane and allowed to slide down from rest. A) It takes the heavier object 5 times longer to reach the bottom of the incline than the lighter object. B) The two objects reach the bottom of the incline at the same time. C) It takes the heavier object 10 times longer to reach the bottom of the incline than the lighter object. D) It takes the lighter object 5 times longer to reach the bottom of the incline than the heavier object. E) It takes the lighter object 10 times longer to reach the bottom of the incline than the heavier object. 10) A 50.0-N box is sliding on a rough horizontal ﬂoor, and the only horizontal force acting on it is 10) friction. Youobserve that at one instant the box is sliding to the right at 1.75 m/s and that it stops in 2.25 s with uniform acceleration. What magnitude force does friction exert on this box? A) 3.97 N B) 490 N C) 8.93 N D) 38.9 N E) 50.0 N 2 11) 15) Bumpers on cars are not of much use in a collision. Tosee why, calculate the average force a11) bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.) A) 6.5 ×10 N B) 5.4 ×10 N C) 1.6 ×10 N D) 3.2 ×10 N 4 E) 1.8 ×10 N 12) A 10,000-kg rocket blasts off from earth with a uniform upward acceleration of 2.00 m/s and 12) feels no air resistance. The upward thrust force its engines must provide during this acceleration is closest to A) 78,000 N. B) 20,000 N. C) 118,000 N. D) 980,000 N. 13) A driver in a1000 kg car traveling at20 m/sslams on the brakes and skids to a stop. If the 13) coefﬁcient of friction between the tires and the horizontal road is 0.80, how long will the skid marks be? A) 26 m B) 24 m C) 33 m D) 21 m 14) A 6.0 kg box slides down an inclined plane that makes an angle of 39° with the horizontal. If th14) coefﬁcient of kinetic friction is0.19, at what rate does the box accelerate down the slope? A) 5.5 m/s2 B) 6.2 m/s2 C) 4.7 m/s 2 D) 5.2 m/s 2 15) A 250-kg crate is on a rough ramp, inclined at 30° above the horizontal. The coefﬁcient of kinet15) friction between the crate and ramp is 0.22. A horizontal force of 5000 N is applied to the crate, pushing it up the ramp. What is the acceleration of the crate? A) 12 m/s2 B) 10 m/s 2 C) 13 m/s2 D) 8.4 m/s 2 E) 3.4 m/s2 16) An 80.0-kg object is falling and experiences a drag force due to air resistance. The magnitude o16) this drag force depends on its speed, v, and obeys the equation Fdrag = (12.0 N∙ s/m)v +(4.00 N∙ s /m )v . What is the terminal speed of this object? A) 47.3 m/s B) 34.2 m/s C) 12.6 m/s D) 6.45 m/s E) 72.2 m/s 17) The International Space Station has a mass of 1.8×10 kg. A 70.0-kg astronaut inside the station 17) 2 pushes off one wall of the station so she accelerates at 1.50 m/s . What is the magnitude of the acceleration of the space station as the astronaut is pushing off the wall? Give your answer relative to an observer who is space walking and therefore does not accelerate with the space station due to the push. A) 5.8 ×10-4m/s 2 B) zero C) 3.9 ×10-3m/s 2 2 D) 1.50 m/s E) 4.7 ×10-4m/s 2 3 18) The ﬁgure shows two 1.0 kg-blocks connected by a rope. A second rope hangs beneath the 18) lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at 2.3 m/s by force F . What is the tension at the top end of rope 1? A) 15 N B) 2.9 N C) 3.5 N D) 18 N 19) A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface as shown in 19) the ﬁgure. The 6.00-kg block is being pushed by a horizontal 20.0-N force as shown. What is the magnitude of the force that the 6.00-kg block exerts on the 4.00-kg block? A) 4.00 N B) 20.0 N C) 10.0 N D) 8.00 N E) 6.00 N 4 20) Two blocks are connected by a string that goes over an ideal pulley as shown in the ﬁgure. Block 20) A has a mass of 3.00 kg and can slide over a rough plane inclined 30.0° to the horizontal. The coefﬁcient of kinetic friction between block A and the plane is 0.400. BlockB has a mass of 2.77 kg. What is the acceleration of the blocks? A) 5.35 m/s 2 B) 3.12 m/s 2 C) 0.392 m/s 2 2 D) 0.00 m/s E) 1.96 m/s 2 21) A car travels at a steady 40.0 m/s around a horizontal curve of radius 200 m. What is the 21) minimum coefﬁcient of static friction between the road and the car's tires that will allow the car to travel at this speed without sliding? A) 0.736 B) 0.816 C) 0.662 D) 1.23 E) 0.952 22) A car enters a 300-m radius horizontal curve on a rainy day when the coefﬁcient of static friction 22) between its tires and the road is 0.600. What is the maximum speed at which the car can travel around this curve without sliding? A) 33.1 m/s B) 42.0 m/s C) 37.9 m/s D) 29.6 m/s E) 24.8 m/s 23) A 1000-kg car is slowly picking up speed as it goes around a horizontal curve whose radius is 23) 100 m. The coefﬁcient of static friction between the tires and the road is 0.350. At what speed will the car begin to skid sideways? A) 35.0 m/s B) 34.3 m/s C) 23.6 m/s D) 9.25 m/s E) 18.5 m/s 24) A 600-kg car is going around a banked curve with a radius of 110 m at a speed of 24.5 m/s. 24) What is the appropriate banking angle so that the car stays on its path without the assistance of friction? A) 60.9° B) 56.2° C) 33.8° D) 29.1° E) 13.5° SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 25) A Ferris wheel has diameter of 10 m and makes one revolution in 8.0 seconds. A person 25) weighing 670 N is sitting on one of the benches attached at the rim of the wheel. What is the apparent weight (that is, the normal force exerted on her by the bench) of the person as she passes through the highest point of her motion? 5 26) A 50.0-kg box rests on a horizontal surface. The coefﬁcient of static friction between the 26) box and the surface is 0.300 and the coefﬁcient of kinetic friction is 0.200. What is the friction force on the box if (a) a horizontal 140-N push is applied to it? (b) a horizontal 175-N push is applied to it? 27) A construction worker pulls a box of tools on a smooth horizontal ﬂoor with a force of 27) 100 N in a direction of 37.0° above the horizontal. The mass of the box and the tools is 40.0 kg. (a) Draw a free-body diagram for the box. (b) Calculate the acceleration of the box. (c) How hard does the ﬂoor push up on the box? 28) The graph in the ﬁgure shows the x component of the acceleration of a 2.4-kg object as a 28) function of time (in ms). (a) At what time(s) does thex component of the net force on the object reach its maximum magnitude, and what is that maximum magnitude? (b) What is thex component of the net force on the object at timet= 0.0 ms and at t= 4.0 ms? 6 Answer Key Testname: PHYS211-EXAM2-REVIEW 1) D 2) B 3) C 4) D 5) D 6) C 7) A 8) A 9) B 10) A 11) C 12) C 13) A 14) C 15) D 16) C 17) A 18) D 19) D 20) C 21) B 22) B 23) E 24) D 25) 460 N 26) (a) 140 N (b) 98.0 N 27) (a) The box is acted on by the force of gravity which points downward toward the center of the earth. The normal force is directed toward the box perpendicular to the surface of the ﬂoor. The pulling force is directed away from the box at an angle 37.0 degrees above the horizontal. 2 (b) 2.00 m/s (c) 332 N 28) (a) At 3.0 ms, 48 N (b) 12 N,-24 N 7

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