An electric toy car with a mass of $2 kg$ is powered by a motor with a voltage of $4 V$ and a current supply of $9 A$ . How long will it take for the toy car to accelerate from rest to $3 m/s$ ?

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Answer 1 · 2016-03-19T03:04:17

$0.25 "s"$

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

$P = IV$

$= (4 "V") * (9 "A")$

$= 36 "W"$

The change in kinetic energy for the car is

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

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

$= 9 "J"$

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

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

$= frac{9 "J"}{36 "W"}$

$= 0.25 "s"$

An electric toy car with a mass of 2 kg2 kg is powered by a motor with a voltage of 4 V4 V and a current supply of 9 A9 A. How long will it take for the toy car to accelerate from rest to 3 m/s3 m/s?