# 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?

Nov 13, 2016

Given

$V \to \text{voltage supplied to motor of toy car} = 4 V$

$I \to \text{current supplied to motor of toy car} = 2 A$

$v \to \text{velocity gained by the car } = 3 \frac{m}{s}$

$m \to \text{mass of thecar } = 5 k g$

Let time taken to gain the velocity be t sec

Now $\text{Power} \left(P\right) = I \times V = 2 \times 4 W = 8 W$

The electrical energy spent in t sec will go to increase the velocity of the car from zero to $3 \frac{m}{s}$.

So

$P \times t = \frac{1}{2} \times m \times {v}^{2}$

$\implies 8 \times t = \frac{1}{2} \times 5 \times {3}^{2}$

$\implies t = \frac{5 \times 9}{2 \times 8} = 2.8125 s$