please do parts a-e Homework #7 (Ch 10: Rotation of a Rigid Object) Begin Date:

Question

please do parts a-e

Homework #7 (Ch 10: Rotation of a Rigid Object) Begin Date: 9 16 2017 12.0000 AM-Dae late:mlsoomli s900PM End Date 12/20/2017 12:00:00 AM (119%) Problem 3: During a very quick stop, a car decelerates at 6.8 m/s Assume the forward motion of the car corresponds to a they do not slip on the pavement) positive direction for the rotation of the tires (and that Randomized Variables a,-68 m/s2 r=0.275 m tus -96 rad's i à 20% Part (a) What is the angular acceleration of its tires in rada. assuming they have a fadius of 0.275 m and do not slip on the pavement? 20% Part (b) How many revolutions do the tires make before coming to rest, given then intial anzular velocity is 96 rads? tus tial tial 20% Part (c) How long does the car take to stop completely in seconds? 20% Part (d) What distance does the car travel in this time meters? a 20% Part (e) what was the car's initial speed in ms? Grade Summary Deducho Potential1005 cosc cotanO asino acos) atanO acotan) sinh) cosh) tanhOcotanhß " DegreesRadians per attempt deased Hist

Explanation / Answer

part(a)

angular acceleration alpha = at/r

at = tangential accelration

r = radius of the wheel

angular acceleration alpha = 24.73 rad/s^2

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part(b)

w^2 - wo^2 = 2*alpha*theta

w = final angular speed = 0

0^2 - 96^2 = -2*24.73*theta

angle rotated theta = 186.33 rad

number of rotations = theta/(2pi) = 29.6 revolutions

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part(c)

alpha = (w - wo)/t

-24.73 = (0-96)/t

time taken to stop = 3.88 s

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part(d)

distance d = r*theta = 0.275*186.33 = 51.24 m

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part (e)

car's initial speed vo = r*wo = 0.275*96 = 26.4 m/s

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