Question

A car goes from 10 to 20 m/s in 4 seconds. How far has it moved in that time?

Answer 1

Car has moved `60m`.

Explanation:

If initial velocity is `u` and final velocity `v` (at a uniform acceleration) in time `t`,

then acceleration `a` is given by `v=u+at` i.e. `a=(v-u)/t`

and distance is given by `v^2-u^2=2aS`

Here `u=10m/s`, `v=20m/s` and `t=4s`

which gives us `a=(20-10)/4=10/4=5/2m/s^2`

Hence `2xx5/2xxS=20^2-10^2`

or `5S=400-100=300`

i.e. `S=300/5=60m`

Additional information `-` Another important relation is `S=ut+1/2at^2` and here `S=10xx4+1/2xx5/2xx4^2`

= `40+20=60m`