Popular in general physics 1- mechanics
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This 9 page Class Notes was uploaded by Shelby Logsdon on Sunday January 11, 2015. The Class Notes belongs to phys 114 at University of Washington taught by kazumi tolich in Winter2015. Since its upload, it has received 294 views. For similar materials see general physics 1- mechanics in Physics at University of Washington.
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Date Created: 01/11/15
Phys 114 1515 Clicker registration httbscatalvstuweduwebdsurvevktolich254782 exam 1 jan 30 exam 2 feb 24 nal mar 17 230420 study center PAB AM018 lecture chapter 11 and 12 scienti c method is a careful application of experience and reason to answer questions introduced in the 16th century by galileo 5 steps to scienti c method 1 recognize a problem 2 form a hypothesis Educated suggestion that is experimentally veri able 3 predict consequences of hypothesis 4 perform experiments to test predictions if experiment disagrees w predictions must go back to step 2 5 formulate theory simplest rule that organizes hypothesis prediction and outcome only if experiment agrees w predictions Theory is a very strong statement means it has not been disproven w experiments Theory cannot be proven to be certainly true Theory can be proven to be wrong UNIT a standard relative to which a quantity such as length is measured Ex Inches pounds miles kilometers SI unts length in meters mass in kilograms time in seconds electric current in amps temp in kelvin amount in mol luminosity on candela Length distance between two points Mass quantitative measure of inertia Lecture chapter 13 18 Dimension physical nature of a quantity dimension of length L feet meters inches etc dimension of mass M kiograms tonne slug etc two quantities can only be added or subtracted if they have the same dimensions the terms on both sides of an equations must have the same dimensions Scienti c notation power of 10 100010x10x1010quot3 multiplication and division in multiplication exponents are added in division exponents are subtracted Conversion of units your employer sends you on a trip to a foreign country where the road signs give distances in kilometers and the automobile speedometers are calibrated in kilometers per hour If you drive 90 kmh how fast are you going in a meters per second 1hr3600s 1000m1km 90kmhr90kmhr1hr360051000m1km25ms b miles per hour 1mi1609km 90kmhr90kmhr1mile1609km56mihr a literL is the volume of a cube that is 10 cm by 10cm by 10cm if you drink 1 L of water how much volume in cubic centimeters and in cubic meters would it occupy in your stomach aquot310cmquot3 10quot3 cmquot3 convert to mquot3 10quot3cmquot310quot2 m1cmquot3 10quot3cmquot310quot6mquot31cmquot310quot3 mquot3 mary is driving in a straight line at 60mph nate is driving at a velocity 2500 micrometersms slower than mary in the same direction How fast is nate driving in ms express in scienti c notation Mary speed 60 milehr 1609 km mile 10quot3 m 1 km 1 hr3600 s2682 ms Nate speed Mary speed 2500 micrometers ms Mary speed 25x10quot3 mcmms10quot6mmcm1 ms10quot3s mary speed 25 ms 262 ms 25ms 243 ms 243x10 ms Order of magnitude calculations in doing rough calculations or order of magnitude calculations we sometimes round off a number to the nearest power of 10 the height of an ant might be 8x10quot4 m or approximately 10quot3 m the order of magnitude of an ant39s height is 10quot3 m Ex What thickness of rubber tread is worn off the tire of your automobile as it travels 1km 6mi Thickness of tread of a new tire 1 cm Distance to wear out new tire 100000 km 1cm of wear 100000km of travel 1x10quot7 m of wearkm Ex Estimate the number of grains of sand on a beach Size of beach 1 km long 100 m wide 1 m deep Diameter of grain of sand 1mm Volume of beach V Number of grains N Volume of single grain G VNXG G 43piRquot3 V 1X10A3 X 100m X 1m 4pi 5x10quot3mquot3 10quot14 Vector and scalar quantities A vector quantity has a magnitude and direction 0 Displacement m how far something moved in what direction 0 Velocity ms how fast something is moving in what direction 0 Acceleration msquot2 how fast velocity is changing in what direction A scalar quantity has only magnitude 0 Time 5 how long 0 Temperature k how hot something is 0 Mass kg how much stuff there is Lecture chapter 21 to 26 Coordinate system and position A coordinate system de nes the position of an object De ne origin and positive direction Displacement is the difference in the initial and nal positions Change in X x naxinitial Displacement is a vector quantity Total distance traveled is total length of travel Distance is a scalar quantity no negative Average velocity and average speed Average velocity is de ned to be xfxitfti Average speed of the trip is de ned to be total distancechange in time Instantaneous velocity and speed Instantaneous velocity in the x direction is de ned to be lim as change in time goes to zero of change in xchange in time Instantaneous speed is the magnitude of the velocity Instantaneous vs average speed Why is instantaneous speed more interesting to the highway patrol than average speed 0 Suppose you drive 100km in one hour your average speed would be 100kmhr o How likely is it that you travel 100kmhr the whole time Motion with constant velocity If the velocity is constant instantaneous at any time is equal to the aveage velocity For a particle with an initial position and a constant velocity the nal position as a function of time is given by X xinitia vt Average and instantaneous accelerations Acceleration is the rate of change of velocity or how quickly velocity is changing Average acceleration in the x direction is de ned to be vfvitfti Speed is absolute value of velocity When direction of acceleration and velocity are the same object is speeding up When direction of acceleration and velocity are opposite object is slowing down Acceleration and force Acceleration is caused by force Motion w constant acceleration For an object with an initial position xO initial velocity vO and a constant acceleration a o The velocity v as a function of time t is given by vv0 at o The position x as a function of time is given by xx0 v0t12atquot2 For an object with a initial velocity vO and a constant acceleration a since velocity varies linearly in time 0 During the period whenan object accelerates from vO to its nal veoctyv its average velocity is given by vav12v0at Ex A motor cycle is moving at v0300 ms when the rider applies the brakes giving the motorcycle a constant deceleration At t130 s after braking begins the speed decreases to v1150ms what distance does the motorcycle travel from the instant braking begins until it comes to rest t00 t130 s v0300ms v1150ms v20 v1 at vO a V1V0t1 1 v2quot2 vOquot22achange in x change in x v2quot2 vOquot22at2v1v0 300msquot22 30s1SO300 90 m Ex At t0 a ball initially at rest starts to roll down a ramp with constant acceleration Suppose it moves 1 foot between t0 and t1 sec how far does it move between t1 and t2 sec Xx0 v0t12atquot2 X00 VOt0 X12atquot2 1ft12a1squots A2ftsquot2 X2512atquot2122ftsquot225quot2 XZsx1s4ft1ft3 ft Lecture ch 27 Free fall The motion of an object falling freely under only the in uence of gravity Without air resistance objects of different weight fall with the same downward acceleration An object is in free fall from the time it is released until it lands whether it is dropped from rest thrown downward or thrown upward Acceleration due to gravity g The acceleration due to gravity is constant at g 981 msquot2 Free faing equations For a free faing object the acceleration is g de ning upward to be the positive x direction For a free falling object with an initial position x0 and initial velocity VO Ex A monkey drops from a tree limb to grab a piece of fruit on the ground 180 m below Neglect the effects of air resistance A How long does it take the monkey to reach the ground X XO VOt 1thquot2 X 0 V0 0 12gtquot2X0 Tquot22XOg T sqrt2X0g sqrt 2180m981mSquot2 T sqrt 606 s B How fast is the monkey moving just before it reaches the ground VV0gt V00 vgt v 981msquot2 6065 594 ms Speed 594ms Alternate solution d displacement VA2 VOquot2ng VO0 Vquot22gX0 V sqrt2981msquot2180m 594ms Speed 594ms Returning speed When a particle thrown upward with an initial velocity v0 returns to the initial height what is its velocity When it comes back it is falling down with the same speed Ex In a jump a springbok leaves the ground at a speed of VO 600 ms A What maximum height above the ground does the springbok attain ddispacement Vquot2V0quot22gd Vquot20 DV0quot22g xX0V0quot2Zg x00 x 600msquot22982msquot2 184 m B How long does it take the springbok to attain this height VV0gt V0 gtV0 TV0g 600mS981msquot2 6125 C What is the springboks velocity when it is x125m above the ground Vquot2V0quot22gd VsqrtV02gd sqrt600msquot22981msquot2125m 339ms D At what times is the springbok 125 m above the ground VV0gt tV0Vg Moving up t 600ms339ms 981msquot22555 Moving down t600ms339ms981msquot2958 5 Ex A tennis ball is hit straight up at V0 200 ms from the edge of a sheer cliff Ignore effects of air resistance A How fast is the ball moving when the ball passes the original height from which it was hit 20ms B If the cliff is 300 m high how long will it take the ball to reach the ground level X X0 V0t12gtquot2 12gtquot2V0txx0 Use quadratic formula Xb sqrtbquot24ac2a TV0l sqrtlvloquot2Zgxx0g T 524s choose pos time C What total distance did the ball travel Vquot2V0quot22gd at max height Vquot2 0 2gdV0quot2 dv0quot22g Total distance 2dx0 2V0quot22g X0 708 m