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

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Answer 1 · 2016-03-19T03:08:03

$0.35 s$ $0.35 "s"$

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

$P = I V$ $P = IV$

$= (2 V) \cdot (5 A)$ $= (2 "V") * (5 "A")$

$= 10 W$ $= 10 "W"$

The change in kinetic energy for the car is

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

$= 1/2 (7 "kg") ((1 "m/s")^2 - (0 "m/s")^2)$

$= 3.5 "J"$

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

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

$= frac{3.5 "J"}{10 "W"}$

$= 0.35 "s"$

An electric toy car with a mass of 7 kg7kg7 kg is powered by a motor with a voltage of 2 V2V2 V and a current supply of 5 A5A5 A. How long will it take for the toy car to accelerate from rest to 1 m/s1ms1 m/s?