Question

Is it reasonable that a 30-kg child could run fast enough to have 100 J of kinetic energy?
(A). Yes, this is reasonable
(B). No, this is not reasonable

Answer 1

Answer:

A.) Yes, this is reasonable

Explanation:

The formula for kinetic energy states $E_k=\frac{1}{2}mv^2$:

$E_k=100J\\m=30kg$

Rewrite the formula to solve for v:

$v=\sqrt(\frac{2E_k}{m})\\v=\sqrt(\frac{(2)(100J)}{30kg})\\v=\sqrt(6.67\frac{m^2}{s^2})\\v=2.58\frac{m}{s}$

$2.58\frac{m}{s}$ translates to approximately 5.77 mph.  Which seems reasonable enough for a child.