An electric toy car with a mass of $2 k g$ $2 kg$ is powered by a motor with a voltage of $5 V$ $5 V$ and a current supply of $3 A$ $3 A$ . How long will it take for the toy car to accelerate from rest to $\frac{8}{3} \frac{m}{s}$ $8/3 m/s$ ?

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Answer 1 · 2016-03-20T02:49:36

$0.474 s$ $0.474 "s"$

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

$P = I V$ $P = IV$

$= (5 V) \cdot (3 A)$ $= (5 "V") * (3 "A")$

$= 15 W$ $= 15 "W"$

The change in kinetic energy for the car is

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

$= 1/2 (2 "kg") ((8/3 "m/s")^2 - (0 "m/s")^2)$

$= 7.11 "J"$

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

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

$= frac{7.11 "J"}{15 "W"}$

$= 0.474 "s"$

An electric toy car with a mass of 2 kg2kg2 kg is powered by a motor with a voltage of 5 V5V5 V and a current supply of 3 A3A3 A. How long will it take for the toy car to accelerate from rest to 8/3 m/s83ms8/3 m/s?