Question

An electric toy car with a mass of `2 kg` is powered by a motor with a voltage of `4 V` and a current supply of `2 A`. How long will it take for the toy car to accelerate from rest to `3 m/s`?

Answer 1

I tried this:

Explanation:

We can say that the power of the motor will be:

`P=VI=4*2=8W`

I would then use the theorem of Work `W` and Kinetic Energy `K` to write:

`W=DeltaK`

`W=1/2mv_f^2-1/2mv_1^2`

dividing both sides by the time we get:

`1/tW=1/t(1/2mv_f^2-1/2mv_1^2)`

`P=1/t(1/2mv_f^2cancel(-1/2mv_1^2))`

because the toy car stars from rest (`v_i=0`).

so we get:

`8=1/t*1/2*2*3^2`

rerranging:

`t=9/8=1.125s`