Question

An electric toy car with a mass of `15 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 `9 m/s`?

Answer 1

The time is `=10.85s`

Explanation:

The power is

`P=UI`

The voltage is `U=8V`

The current is `I=7A`

The power is

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

The kinetic energy of the car is

`E=1/2mv^2`

The mass is `m=15kg`

The speed is `v=9ms^-1`

so,

`E=1/2*15*(9)^2=607.5J`

Let the time `=(t)s`

`E=Pt`

`t=E/P=(607.5)/56=10.85s`