A man pushes a 15kg box of books 2.0m up a 37∘ incline into the back of a moving van. The box moves at a constant velocity if you push it with a force of 95N. Find the work done by gravity on the box. Take (g=10m/s2)
The correct option is A−180J FBD of system is
From FBD of the block, we have the component of weight down the incline plane as mgsinθ and the displacment is up the incline plane d=2.0m, the other component of weight will be perpendicular to plane mgcosθ.
Now here the work done will be due to the force component along the plane only which is, F=mgsinθ. The angle between F and d is 180o
Hence work done by gravity will be only due to the force along the incline plane Wg=→F.→s=(mgsin37o)×2×cos180o