Physics

A 855 N crate rests on the floor.

a) How much work is required to move it at constant speed 7.7 m along the floor against a friction force of 180 N?

b) How much work is required to move it at constant speed 7.7 m vertically?

I really NEED help I am very lost with physics!!!!

asked by Jen
  1. a) work= force applied*distance
    and force applied has to equal friction.
    b) work=increase in gravitational PE
    = mass*g*height

    Very Lost? There is no reason for that. Go to your nearest college bookstore, or Barnes Noble, and examine the Schaum's Outline Series, xxxx Physics. There are several in that series, I like the Physics for engineers and scientists, but frankly, it is heavy in calculus...most like the college physics issue. They are filled with worked example problems, with explainations. They are priced very reasonable.

    posted by bobpursley
  2. I figured A out it was 1386 J, but I can not figure out B I used 855X9.8x7.7 and that's not right can you tell me where I went wrong?

    posted by Jen
  3. well, there is no answer for b, unless you know the height. As height changes, gravitational potenial energy changes, so you had to put more energy in. IF this is all there is to the problem, you cannot do it, the problem is deficient. 7.7 is the speed. you cannot get height frm speed without time...however, you can get the POWER in watts used (Power=work/time)
    Power= m*g*speed
    and
    work= Power*time but you have to have again height to get the time.

    posted by bobpursley
  4. 7.7 is the height in this problem not the speed.

    posted by Nate

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