Question

I'm not sure how to approach this...
"I exert a force of F on a box of mass 20kg as it moves from x=2m to x=7m as its speed goes from 1m/s to 2m/s. The force makes an angle of 37 degrees with the horizontal. If I did 160J of work, what was the magnitude of the force F? If the only other force doing work was friction, how much work did friction do?"

Answer 1

you can use the work energy theorem to find out what is the NET work done (total work done by you ANd friction together)

you can use w = f.x to find out how much work YOU did.. but you already know that.. which is 160.. so you can find f

now once you know how much work you did.. and you know what is the total work done you can now find out what is the work done by friction!

Answer 2

So, if I use w=fdcos37 and solve for f, that is the force used?

Answer 3

yes!..

Answer 4

Ah, I was afraid I had to do something with the speed changes. Thank you!

Answer 5

you have to.. for the friction part you need to!