An electric toy car with a mass of $6 k g$ $6 kg$ is powered by a motor with a voltage of $7 V$ $7 V$ and a current supply of $3 A$ $3 A$ . How long will it take for the toy car to accelerate from rest to $4 \frac{m}{s}$ $4 m/s$ ?

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Answer 1 · 2016-03-19T04:09:26

$2.29 s$ $2.29 "s"$

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

$P = I V$ $P = IV$

$= (7 V) \cdot (3 A)$ $= (7 "V") * (3 "A")$

$= 21 W$ $= 21 "W"$

The change in kinetic energy for the car is

$Delta "KE" = 1/2 m (v^2 - v_0^2)$

$= 1/2 (6 "kg") ((4 "m/s")^2 - (0 "m/s")^2)$

$= 48 "J"$

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

$t = frac{Delta "KE"}{P}$

$= frac{48 "J"}{21 "W"}$

$= 2.29 "s"$

An electric toy car with a mass of 6 kg6kg6 kg is powered by a motor with a voltage of 7 V7V7 V and a current supply of 3 A3A3 A. How long will it take for the toy car to accelerate from rest to 4 m/s4ms4 m/s?