Question

A 22 kg sled is pushed for 5.2 m with a horizontal force of 20 N, starting from rest. Ignore friction. Find the final speed of the sled.

Answer 1

Note that this force does $20 \, N \cdot 5.2 \, m = 104 \, J$ of work.  Then, by conservation of energy, we have that:

$\frac{mv^2}{2} = 104 \, J$

Substituting $m=22 \, kg$, we see that:

$11v^2 \, kg = 104 \, J$

Then, dividing by $11$ and taking the square root, we see that:

$v=~3.1 \, m/s$