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 `5 A`. How long will it take for the toy car to accelerate from rest to `2 m/s`?

Answer 1

The time is `=0.17s`

Explanation:

Voltage is `U=7V`

Current is `I=5A`

The power is

`P=UI=7*5=35W`

Velocity is `v=2ms^-1`

Mass is `m=3kg`

The kinetic energy is

`KE=1/2mv^2=1/2*3*(2)^2=6J`

But,

`E=P*t`

The time is `t=E/P=(6)/35=0.17s`