Physics Work Questions

Question

9.A sled is pulled with a rope at an angle of 23° above the horizontal. The tension on the rope is 47 N. How much work is done to move the sled horizontally 5.0 m?

10. A girl pulls a wagon along a level path for a distance of 55 m. The handle of the wagon makes a 25° angle with the horizontal. If she pulls the handle with the force of 60 N, how much work is done?

Answer 1

For problem 9:

W = F•d

But, the direction of the travel is in the x-direction (the "d" in the equation) so only the portion of the 47N that is being applied in the x-direction contributes to the work being done.

Fx = 47•cos(23°) = 43.264 N

So W = (43.264)(5) = 216.32 Nm (or joules) but since there are only 2 sig figs in the "givens" we would round the answer to 220 Nm (or 220 j)

For problem 10:

This is the same type of problem. Only the portion of the 60N that is applied in the x-direction contributes to the work done in the x-direction. so Fx = 60•cos(25°) = 54.378 N and W = F•d = (54.378)(55) = 2990.82 Nm. Again, we need to round based on the number of sig figs. This problem has only 1 sig fig in the 60 N so our answer needs to have 1 sig fig, so we round to 3000 Nm (or 3000 j)