A 17.2 kg block is dragged over a rough, horizontal surface by a constant force

Question

A 17.2 kg block is dragged over a rough, horizontal surface by a constant force of 117 N acting at an angle of angle 35? above the horizontal. The block is displaced 78.4 m and the coefficient of kinetic friction is 0.151.

See Picture above.

1) Find the work done by the 117 N force. The acceleration of gravity is 9.8m/s^2.

2)Find the magnitude of the work done by the force of friction.

A 17.2 kg block is dragged over a rough, horizontal surface by a constant force of 117 N acting at an angle of angle 35? above the horizontal. The block is displaced 78.4 m and the coefficient of kinetic friction is 0.151. See Picture above. 1) Find the work done by the 117 N force. The acceleration of gravity is 9.8m/s^2. 2)Find the magnitude of the work done by the force of friction.

Explanation / Answer

a) W = F.d cos theta
so,
W = 117*78.4* cos ( 35)
W= 7514 J

b)
f = mu* N = mu* [M*g-F sin theta)
so,
f = 0.151 * [17.2*9.8 -117 sin 35]

so,
work due to friction ,
Wf = f* d
so,
Wf = - 0.151 * [17.2*9.8 -117 sin 35] *78.4
so,
Wf=-1201 J

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