What maximum power must the motor provide?

[stupif]

1. A loaded ore car has a mass of 950 kg and rolls on rails with negligible friction. It starts from rest
and is pulled up a mine shaft by a cable connected to a winch. The shaft is inclined at 30.0°
above the horizontal. The car accelerates uniformly to a speed of 2.20 m/s in 12.0 s and then
continues at constant speed. (a) What power must the winch motor provide when the car is
moving at constant speed? (b) What maximum power must the motor provide? (c) What total
energy transfers out of the motor by work by the time the car moves off the end of the track,
which is of length 1 250 m?
( Ans : (a) 10.2 kW (b) 10.6 kW (c) 5.82 MJ )

2，power = (mass x acceleration x distance)/ time
= (950kg x (2.2/12=0.183m/s^2) x distance )/ 12s

how to find the distance??

The Attempt at a Solution

 

[Doc Al]

I'm not sure which part you are attempting to solve. Starting with part a, what's the force exerted by the cable? What power must it exert?

 

[stupif]

i am finding this answer (a) What power must the winch motor provide when the car is
moving at constant speed?

 

[Doc Al]

So answer my question: What force is exerted by the cable? And how does force relate to power?

 

[stupif]

pulling force...power = workdone / time, workdone = force x distance

 

[Doc Al]

pulling force...power = workdone / time, workdone = force x distance

OK, so what's the pulling force?

 

[stupif]

dont know

 

[Doc Al]

dont know

You'll have to figure it out. Hint: constant speed.