Question

The mass of cyclist together with the bike is $90kg$. Calculate the increase in kinetic energy if the speed increases from $6.0km/h$ to $12km/h$.

Answer 1

The final velocity is given as,

$v_f=12\times \frac{5}{18}$

$=\frac{10}{3}m/s$

The initial velocity is given as,

$v_i=6\times \frac{5}{18}$

$=\frac{5}{3}m/s$

The increase in kinetic energy is given as,

$\Delta KE=\frac{1}{2}m\left({v_f}^2-{v_i}^2\right)$

$=\frac{1}{2}\times 90\left({\left(\frac{10}{3}\right)}^2-{\left(\frac{5}{3}\right)}^2\right)$

$=375J$

Thus, the increase in kinetic energy is $375J$.