Question

An electric toy car with a mass of `1 kg` is powered by a motor with a voltage of `12 V` and a current supply of `7 A`. How long will it take for the toy car to accelerate from rest to `5 m/s`?

Answer 1

The time is `=0.15s`

Explanation:

The voltage is `U=12V`

The current is `I=7A`

The power of the motor is

`P=UI=12*7=84W`

Velocity is `v=5ms^-1`

Mass is `m=1kg`

The kinetic energy of the car is

`KE=1/2mv^2=1/2*1*(5)^2=12.5J`

But,

`E=P*t`

The time is `t=(12.5)/84=0.15s`