A 700 kg elevator starts from rest. It moves upward for 4.00 s with constant acc

Question

A 700 kg elevator starts from rest. It moves upward for 4.00 s with constant acceleration until it reaches its cruising speed, 1.75 m/s.

(angel) What is the average power of the elevator motor during this period?

How does this power compare with the motor power when the elevator moves at its cruising speed?

Pcruising = W

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 26.5

Explanation / Answer

power =energy/time =(mgh+0.5mv^2)/time

also 1.75/4 =acc =0.4375

....

hence 1.75^2 =2*0.4375*s

hence s =3.5

hence (mgh+0.5mv^2)/time =700(9.8*3.5+0.5*1.75^2)/4 =6270.5 W

.....

at cruising speed power =Fs =700*9.8*1.75 =12005 W

.........................

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