# An electric toy car with a mass of 3 kg is powered by a motor with a voltage of 3 V and a current supply of 4 A. How long will it take for the toy car to accelerate from rest to 1 m/s?

Dec 5, 2017

The time is $= 0.125 s$

#### Explanation:

The power is

$P = U I$

The voltage is $U = 3 V$

The current is $I = 4 A$

The power is

$P = U I = 3 \cdot 4 = 12 W$

The kinetic energy of the car is

$E = \frac{1}{2} m {v}^{2}$

The mass is $m = 3 k g$

The speed is $v = 1 m {s}^{-} 1$

so,

$E = \frac{1}{2} \cdot 3 \cdot {\left(1\right)}^{2} = 1.5 J$

Let the time $= \left(t\right) s$

$E = P t$

$t = \frac{E}{P} = \frac{1.5}{12} = 0.125 s$