An electric toy car with a mass of $4 kg$ is powered by a motor with a voltage of $6 V$ and a current supply of $7 A$ . How long will it take for the toy car to accelerate from rest to $8 m/s$ ?

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Answer 1 · 2016-03-20T02:33:04

$3.05 "s"$

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

$P = IV$

$= (6 "V") * (7 "A")$

$= 42 "W"$

The change in kinetic energy for the car is

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

$= 1/2 (4 "kg") ((8 "m/s")^2 - (0 "m/s")^2)$

$= 128 "J"$

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

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

$= frac{128 "J"}{42 "W"}$

$= 3.05 "s"$

An electric toy car with a mass of 4 kg4 kg is powered by a motor with a voltage of 6 V6 V and a current supply of 7 A7 A. How long will it take for the toy car to accelerate from rest to 8 m/s8 m/s?