Question

An electric toy car with a mass of `5 kg` is powered by a motor with a voltage of `8 V` and a current supply of `7 A`. How long will it take for the toy car to accelerate from rest to `7 m/s`?

Answer 1

The time is `=2.2s`

Explanation:

The voltage is `U=8V`

The current is `I=7A`

The power of the motor is

`P=UI=8*7=56W`

Velocity is `v=7ms^-1`

Mass is `m=5kg`

The kinetic energy of the car is

`KE=1/2mv^2=1/2*5*(7)^2=122.5J`

But,

`E=P*t`

The time is `t=(122.5)/56=2.2s`