Question

An electric toy car with a mass of `5 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

Given

`V->"voltage supplied to motor of toy car"=4V`

`I->"current supplied to motor of toy car"=2A`

`v->"velocity gained by the car "=3m/s`

`m->"mass of thecar "=5kg`

Let time taken to gain the velocity be t sec

Now `"Power"(P)=IxxV=2xx4W=8W`

The electrical energy spent in t sec will go to increase the velocity of the car from zero to `3m/s`.

So

`Pxxt=1/2xxmxxv^2`

`=>8xxt=1/2xx5xx3^2`

`=>t=(5xx9)/(2xx8)=2.8125s`