contestada

If a motor lifts a 400.-kilogram mass a vertical
distance of 10. meters in 8.0 seconds, the
minimum power generated by the motor is
(1) 3.2 × 10^2 W (3) 4.9 × 10^3 W
(2) 5.0 × 10^2 W (4) 3.2 × 10^4 W

Respuesta :

TaylorBayley
We can work out the gain in GPE of the box. I'm going to take g to be 9.81 however if your qualification takes g to be 10 you'll need to change it in all the workings:

GPE = mgh
= 400 x 9.81 x 10
=39240J

So, the machine has given 39240J of energy to the box.

Therefore the minimum power generated by the motor is:

39240/8=4905W = 4.9 x 10^3 W
Note this is the minimum possible power generated by it and it is almost certain (well completely certain in the real world) that it will generate far more power than that because it will not be 100% efficient.