# An electric toy car with a mass of 1 kg is powered by a motor with a voltage of 6 V and a current supply of 15 A. How long will it take for the toy car to accelerate from rest to 5 m/s?

Mar 20, 2016

$0.139 \text{s}$

#### Explanation:

The power input is the product of the voltage and the current.

$P = I V$

$= \left(6 \text{V") * (15 "A}\right)$

$= 90 \text{W}$

The change in kinetic energy for the car is

$\Delta \text{KE} = \frac{1}{2} m \left({v}^{2} - {v}_{0}^{2}\right)$

= 1/2 (1 "kg") ((5 "m/s")^2 - (0 "m/s")^2)

$= 12.5 \text{J}$

Thus, the time needed is the energy divided by the power.

$t = \frac{\Delta \text{KE}}{P}$

= frac{12.5 "J"}{90 "W"}

$= 0.139 \text{s}$