A box weighing 400 N is pulled up a 40 m incline to a point 1.6 m above its star

Question

A box weighing 400 N is pulled up a 40 m incline to a point 1.6 m above its starting level. The force needed to pull the box is 20 N. Find the work output, the work input, the work to overcome friction, and the efficiency of the machine.

Explanation / Answer

First calculate angle(x) of inclined plane sin(x)=1.6/40=.04 x=2.29 degree component of gravity force along down the plane --> Fdown=400*sin(x)=400*0.04=16N External force to pull mass up= friction +Fdown=20N friction force=20-16=4N so work waste in friction =4*40=160J-------work to overcome friction Net work output=1.6*400=640J--------Work output Net work input=160+640=800J---------Work input so efficiency=640/800=80%------efficiency

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