# 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?

May 16, 2017

To accelerate the object from rest to 1.5$m {s}^{-} 1$ the battery need to do some work on it we can say the work by
$W = \frac{1}{2} m \left({v}_{f}^{2} - {v}_{i}^{2}\right)$
which is ,
$4.5 J$

now the electrical energy is equal to =${i}^{2} R t$ or $V i t$

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

$4.5 = V i t$

so , $\frac{4.5}{7 \cdot 9} = t = 0.07 \sec$