Question

An electric toy car with a mass of `4 kg` is powered by a motor with a voltage of `7 V` and a current supply of `9 A`. How long will it take for the toy car to accelerate from rest to `3/2 m/s`?

Answer 1

To accelerate the object from rest to 1.5`ms^-1` the battery need to do some work on it we can say the work by
`W=1/2m(v_f^2-v_i^2)`
which is ,
`4.5J`

now the electrical energy is equal to =`i^2Rt` or `Vit`

the electrical energy is equal to the mechanical work done , hence

`4.5=Vit`

so , `(4.5)/(7*9)=t=0.07sec`