Question

A student wearing frictionless in-line skates on a horizontal surface is pushed by a friend with a constant force of 45 N. How far must the student be pushed, starting from rest, so that her final kinetic energy is 352 J?

Answer 1

I tried this:

Explanation:

We can use the Theorem of Work (W) and Kinetic Energy (K):

`W=DeltaK=K_f-K_i`

it basically tells us that the work done on our system will show up as change in Kinetic Energy:
We know that the initial Kinetic Energy, `K_i=1/2mv_i^2`, is zero (starting from rest) while the final will be equal to `352J`; Work will be force time displacement. so we get:

`F*d=F_f`

`45d=352`

and so:

`d=352/45=7.8~~8m`