The four wheels of a car have each a mass of 25kg and a radius of 30cm. The car's mass is 1000kg. We neglect the losses due to friction. We assimilate the wheels to homogeneous cylinders.(adsbygoogle = window.adsbygoogle || []).push({});

a) What is the total kinetic energy of the car and the wheels if the speed of the car is 30m/s.

b) What distance will the car travel till it stops going up an incline of 10 degrees if the initial speed is of 30m/s?

For a I did,

Ktot = rotational kinetic energy + linear kinetic energy

= 1/2lw + 1/2mv^2

= (1/2)(4.5)(100)^2 + (1/2)(1100)(30)^2

= 518kJ

For b I thought I could just use "gravitational potential = rotational kinetic energy + linear kinetic energy"

h = xsin10

So mgx = rotational kinetic energy + linear kinetic energy

mgx = 518000

x = -89m

Obviously I did something wrong because I shouldn't be getting a minus...and on top of that I know the answer is 276m.

Any ideas on what I did wrong..or what I might of forgotten to do?

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# Homework Help: Rotational Energy conservation

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