Question

An electric toy car with a mass of `4 kg` is powered by a motor with a voltage of `3 V` and a current supply of `8 A`. How long will it take for the toy car to accelerate from rest to `3 m/s`?

Answer 1

It will take `3s` to accelerate the car.

Explanation:

To accelerate the car to `3m/s` engine has to do work equal to the car's end kinetic energy:

`W=E_k=(mv^2)/2=(4*3^2)/2=2*9=18 [J]`

Now to find the time we have to calculate the engine's power:

`P=U*I=3*8=24[W]`

Finally to calculate the time we have to divide the work/energy by the power:

`t=W/P=18/24=2/3[s]`