Question

An object with a mass of `4 kg` is moving at `7 m/s` over a surface with a kinetic friction coefficient of `1`. How much power will it take to accelerate the object at #4 m/s^2?

Answer 1

386 W

Explanation:

The force you must give, must equilibrate both the inertia force and the friction force:
`F_t= F_i+ F_f= mxxa + m xx g xx mu_f= 4 kg xx 4 m/ s^2+ 4kg xx 9.8 m/s^2 xx 1= 16 N + 39.2 N = 55.2 N`
The power is given by :
`P= F_t xx v= 56 N xx 7 m/s = 386 W`
Because the few significative figures used it has no sense a bigger precision