A concrete block is pulled 7.0 m across a frictionless surface by means of a rope. The tension in the rope is 40 N; and the net work done on the block is 247 J. What angle does the rope make with the horizontal?

Question

SmokeyBrown · Answer

The block is being pulled over a distance of 7.0 meters with a force of 40 N; normally 40 N of force over 7 meters of distance would result in 280 J, but it seems that the net work done on the block is 247 J.

Consider what angle might have led to proportionately less work being done. A hint: you can multiply the expected work by a certain trigonometric function of the angle measure in order to get the actual work; one solution involves working backwards from there in order to find the measure of the angle.

Vocaloid · Answer

For work when the applied force is at an angle:

Work = Fcos(theta)

They give you the work and tension force so you can solve for theta.