An electric toy car with a mass of $4 k g$ $4 kg$ is powered by a motor with a voltage of $4 V$ $4 V$ and a current supply of $9 A$ $9 A$ . How long will it take for the toy car to accelerate from rest to $\frac{7}{2} \frac{m}{s}$ $7/2 m/s$ ?

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Answer 1 · 2017-06-29T05:32:08

The time is $= 0.68 s$ $=0.68s$

The voltage is $U = 4 V$ $U=4V$

The current is $I = 9 A$ $I=9A$

The power of the motor is

$P = U I = 4 \cdot 9 = 36 W$ $P=UI=4*9=36W$

Velocity is $v = \frac{7}{2} m s^{- 1}$ $v=7/2ms^-1$

Mass is $m = 4 k g$ $m=4kg$

The kinetic energy of the car is

$K E = \frac{1}{2} m v^{2} = \frac{1}{2} \cdot 4 \cdot {(\frac{7}{2})}^{2} = \frac{49}{2} J$ $KE=1/2mv^2=1/2*4*(7/2)^2=49/2J$

But,

$E = P \cdot t$ $E=P*t$

The time is $t = \frac{24.5}{36} = 0.68 s$ $t=(24.5)/36=0.68s$

An electric toy car with a mass of 4kg4 kg is powered by a motor with a voltage of 4V4 V and a current supply of 9A9 A. How long will it take for the toy car to accelerate from rest to 72ms7/2 m/s?