Question

An electric toy car with a mass of `2 kg` is powered by a motor with a voltage of `9 V` and a current supply of `7 A`. How long will it take for the toy car to accelerate from rest to `5/2 m/s`?

Answer 1

The time is `=0.1s`

Explanation:

Voltage is `U=9V`

Current is `I=7A`

The power of the motor is

`P=UI=9*7=63W`

Velocity is `v=5/2ms^-1`

Mass is `m=2kg`

The kinetic energy of the car is

`KE=1/2mv^2=1/2*2*(5/2)^2=25/4J`

But,

`E=P*t`

The time is `t=(25/4)/63=0.1s`