Question

An electric toy car with a mass of `7 kg` is powered by a motor with a voltage of `2 V` and a current supply of `2 A`. How long will it take for the toy car to accelerate from rest to `7 m/s`?

Answer 1

The time is `=42.9s`

Explanation:

Voltage is `U=2V`

Current is `I=2A`

The power is

`P=UI=2*2=4W`

Velocity is `v=7ms^-1`

Mass is `m=7kg`

The kinetic energy is

`KE=1/2mv^2=1/2*7*7^2=171.5J`

But,

`E=P*t`

The time is `t=E/P=171.5/4=42.9s`