Question

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

Answer 1

Given,

Mass, $m=m_c+m_b=90kg$

Initial velocity, $u=6km/h=1.666m/sec$

Final velocity, $v=12km/h=3.333m/sec$

Increase in K.E. = Final K.E. - Initial K.E. = $\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^2$

$=\frac{1}{2}\times 90\times (3.333{)}^2-\frac{1}{2}\times 90\times (1.66{)}^2$

$=499.4-124.6$

$=374.8=375$ J