An electric toy car with a mass of $5 k g$ $5 kg$ is powered by a motor with a voltage of $1 V$ $1 V$ and a current supply of $2 A$ $2 A$ . How long will it take for the toy car to accelerate from rest to $\frac{4}{5} \frac{m}{s}$ $4/5 m/s$ ?

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Answer 1 · 2016-03-19T03:03:00

$0.8 s$ $0.8 "s"$

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

$P = I V$ $P = IV$

$= (1 V) \cdot (2 A)$ $= (1 "V") * (2 "A")$

$= 2 W$ $= 2 "W"$

The change in kinetic energy for the car is

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

$= 1/2 (5 "kg") ((4/5 "m/s")^2 - (0 "m/s")^2)$

$= 1.6 "J"$

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

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

$= frac{1.6 "J"}{2 "W"}$

$= 0.8 "s"$

An electric toy car with a mass of 5 kg5kg5 kg is powered by a motor with a voltage of 1 V1V1 V and a current supply of 2 A2A2 A. How long will it take for the toy car to accelerate from rest to 4/5 m/s45ms4/5 m/s?