Barron's 2nd Edition PT1 Q36

Barron's Book

36) This question asks us to determine the work done by the force F. There are multiple ways we can do this problem. Let’s look at some of the simple ways. Refer to problem 35. In problem 35, we found that the force pushing the object up the ramp was 10 N. Work is the dot product of F and d, so we could solve for work by multiplying the force by the length of the ramp.

Where ℓ is length of the ramp, W is work, and F is force

This solution gives us 40 Joules of work done by force F.

Here's another simple solution to this problem. We can solve the problem by setting work equal to the change in gravitational potential energy.

Where U[g] is gravitational potential energy, m is mass, g is acceleration of gravity, and h is height

Next, we'll draw a diagram to find the height at each point.

Where h is height

Finally, we would solve for the change in potential energy.

Where W is work, U[g] is potential energy, m is mass, g is acceleration of gravity, and h is height

This method also results in 40 Joules of work.

Answer: E