An electric toy car with a mass of $1 k g$ $1 kg$ is powered by a motor with a voltage of $2 V$ $2 V$ and a current supply of $7 A$ $7 A$ . How long will it take for the toy car to accelerate from rest to $5 \frac{m}{s}$ $5 m/s$ ?

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Answer 1 · 2016-03-20T02:35:24

$0.893 s$ $0.893 "s"$

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

$P = I V$ $P = IV$

$= (2 V) \cdot (7 A)$ $= (2 "V") * (7 "A")$

$= 14 W$ $= 14 "W"$

The change in kinetic energy for the car is

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

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

$= 12.5 "J"$

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

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

$= frac{12.5 "J"}{14 "W"}$

$= 0.893 "s"$

An electric toy car with a mass of 1 kg1kg1 kg is powered by a motor with a voltage of 2 V2V2 V and a current supply of 7 A7A7 A. How long will it take for the toy car to accelerate from rest to 5 m/s5ms5 m/s?