Question

An electric toy car with a mass of `3 kg` is powered by a motor with a voltage of `7 V` and a current supply of `1 A`. How long will it take for the toy car to accelerate from rest to `5/3 m/s`?

Answer 1

`0.6s`

Explanation:

Electrical power is

`P=IV`

and mechanical power is

`P = E/t`

so

`E/t = IV`

We can work out `E` by

`E = 1/2mv^2 = 1/2 xx 3 xx (5/3)^2 = 4.17J`

Rearrange the equation for time, which we want to find:

`t = E/(IV) = 4.17/(7xx1) = 0.6s`