Question

What is the work done by the force of friction?

A box is on a 15 degree incline, being pulled by a rope that is parallel to the incline. The total mass of the box is 2.834 kg. The box was pulled for a distance of 1 meter. A force sensor calculated the pulling force 1.291 N. My calculations: The total graviton force based on these numbers was calculated to be 27.78 N. The work done by the pulling force is 1.291 J. The work done by the gravitational force is 7.19 J. The expected change in kinetic energy (since the system moves with constant velocity) should be 0.

What is the work done by the frictional force?

I don't understand this because based on the calculations, I am getting it would have to negative (or working in the direction of the pulling force).

Answer 1

work done by pulling force = 1.291 J

work done by gravity = 7.19 J

work done by gravity is positive so block is coming downwards and force is acting along downwards along inclined.

change in kinetic energy is ero so all work

0 = work by gravity + work by pulling force + work by riction

work by riction = - ( work by gravity + work by pulling force)

work done by friction = - (1.291+7.19) J = - 8.481 J.

work done bby friction force is negative and of 8.481J.

I hope you understand.

thanks for asking.

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