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Homework Statement
Three people, each of whom pushes with a force of 130N, can just keep a stalled car (mass 1400kg) moving along a level road. They each push with a force of 140N to get it to a service station 100m away.
Homework Equations
a) How much work do they do in moving the car to the service station?
b) What is the kinetic energy of the automobile on arriving?
c) What is the automobile's speed on arrival?
The Attempt at a Solution
a) I said that: [itex]
Work=[(140N \times 3) - (130N \times 3)] \times 100m=3000J
[/itex], but I'm unsure if I correctly calculated the average force. My thinking was that the car was just moving with 390N of force (130N multiplied by 3 people), so it had no net force and was in constant motion. Once the extra 10N per person of force were applied, the car moved at an accelerated rate, so the net force was 420N-390N=30N. I can't figure out if I'm overthinking this or not.
b) I can't figure out how to get kinetic energy without velocity [itex] (KE= \frac{1}{2}mv^2) [/itex]. I can find the CHANGE in kinetic energy (work), but without knowing how much KE the car had before the 100m stretch of road I can't figure it out.
c) If I can get KE, I can easily solve for v.
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