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?

1 Answer
Andrea B.
Feb 23, 2018

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

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