Question

An electric toy car with a mass of `4 kg` is powered by a motor with a voltage of `4 V` and a current supply of `9 A`. How long will it take for the toy car to accelerate from rest to `7/2 m/s`?

Answer 1

The time is `=0.68s`

Explanation:

The voltage is `U=4V`

The current is `I=9A`

The power of the motor is

`P=UI=4*9=36W`

Velocity is `v=7/2ms^-1`

Mass is `m=4kg`

The kinetic energy of the car is

`KE=1/2mv^2=1/2*4*(7/2)^2=49/2J`

But,

`E=P*t`

The time is `t=(24.5)/36=0.68s`