- #1
san512
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Homework Statement
The average car today has a mass of 1100 kg, and when accelerating from rest, covers 0.25 miles in 15 seconds. Each rim and tire together has a diameter of 46 cm and a mass of 9.1kg. If we agree the rim and tire have the shape of a solid disk that rotates through its geometric center, what would be the kinetic energy of one of the tires, in Joules, at the end of the run?
2. Homework Equations
ke = 1/2 * I * w^2, I=1/2*r^2*m
The Attempt at a Solution
i calculated the moment of inertia to be .24 by I= 9.1kg*.23m^2*.5
I calculated the angular velocity to be 116.59 rad/s by finding the rev/sec and then converting to rad/sec
circum = .23*2*pi = 1.4451m
and the rev: 402.25m/1.4451m = 278 rev. i got 402.25 by converting .25 miles to meters
278/15= 18.5rev/sec
18.5rev/sec* 2*pi = 116.59rad/ sec
in the end i got KE= 1635 j
i don't know if that's right. i also need help applying significant numbers. i don't know whether to apply them towards the final calculation or throughout the conversions
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