Question

An electric toy car with a mass of `5 kg` is powered by a motor with a voltage of `6 V` and a current supply of `12 A`. How long will it take for the toy car to accelerate from rest to `7 m/s`?

Answer 1

The time is `=0.24s`

Explanation:

The power is

`P=UI`

`"Power"="Voltage"xx"Current"`

The voltage is `U=6V`

The current is `I=12A`

The power is

`P=UI=6*12=72W`

The kinetic energy of the car is

`E=1/2mv^2`

The mass of the car is `m=5kg`

The speed is `v=7ms^-1`

so,

`E=1/2*5*(7)^2=35/2J`

Let the time `=(t)s`

`E=Pt`

`"Energy=Power" xx "time"`

The time is

`t=E/P=(35/2)/72=0.24s`