An electric toy car with a mass of $4 kg$ is powered by a motor with a voltage of $15 V$ and a current supply of $15 A$ . How long will it take for the toy car to accelerate from rest to $5 m/s$ ?

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Answer 1 · 2016-03-19T04:06:00

$0.222 "s"$

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

$P = IV$

$= (15 "V") * (15 "A")$

$= 225 "W"$

The change in kinetic energy for the car is

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

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

$= 50 "J"$

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

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

$= frac{50 "J"}{225 "W"}$

$= 0.222 "s"$

Btw there should be some kind of error. A toy car wouldn't have that kind of batteries.

An electric toy car with a mass of 4 kg4 kg is powered by a motor with a voltage of 15 V15 V and a current supply of 15 A15 A. How long will it take for the toy car to accelerate from rest to 5 m/s5 m/s?