Question

A 1200 kg car travel along the road , calculate it's kinetic energy at 54 km/hr

Answer 1

First, convert km/h to m/s:

$$v=54\text{ km/h}·\frac{1000\text{ m/km}}{3600\text{ s/h}}=15\text{ m/s}.$$

The kinetic energy is

$$KE=\frac12mv^2=\frac121200·15^2=135000\text{ J}.$$