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

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Answer 1 · 2017-05-15T14:19:52

I tried this:

We can say that the power of the motor will be:

$P = V I = 4 \cdot 2 = 8 W$ $P=VI=4*2=8W$

I would then use the theorem of Work $W$ $W$ and Kinetic Energy $K$ $K$ to write:

$W=DeltaK$

$W=1/2mv_f^2-1/2mv_1^2$

dividing both sides by the time we get:

$1/tW=1/t(1/2mv_f^2-1/2mv_1^2)$

$P=1/t(1/2mv_f^2cancel(-1/2mv_1^2))$

because the toy car stars from rest ( $v_i=0$ ).

so we get:

$8=1/t*1/2*2*3^2$

rerranging:

$t=9/8=1.125s$

An electric toy car with a mass of 2 kg2kg2 kg is powered by a motor with a voltage of 4 V4V4 V and a current supply of 2 A2A2 A. How long will it take for the toy car to accelerate from rest to 3 m/s3ms3 m/s?