(adsbygoogle = window.adsbygoogle || []).push({}); 1) An 80-N box is pulled 20m up a 30 degree incline by an applied force of 100 N that points upward, parallel to the incline. If the coefficient of kinetic friction between box and incline is 0.220, calculate the change in the kinetic energy of the box.

I made a triangle sketch, obviously, 30 degrees in the lower left corner. One of my big problems is I'm not sure what they mean by "80-N box." Does that mean it's a force of 80 N straight down, or is that like a force perpendicular against the incline? I used muK = Ff-Fn to find an Ff of 80.220 N. Then I did something with FcosΘ=work, and somehow came up with 86.6 J. I really don't know what I'm doing, and I have no correct answer listed anywhere, so I have no direction. Help!

2)A 70kg diver steps off a 10m tower and drops, from rest, straight down into the water. If he comes to rest 5.0m below the surface, determine the average resistance force exerted on him by the water.

I used vf^2=vi^2 + 2ad to get his initial velocity at the water (I got 14 m/s) but after that I'm clueless as to what to do next.

Any help you can provide me would be great, I'm going to re-read the chapter. I've been sick from school for a few days, so I'm really behind and lost here.

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Work & Energy Questions

**Physics Forums | Science Articles, Homework Help, Discussion**