An electric toy car with a mass of $3 k g$ $3 kg$ is powered by a motor with a voltage of $7 V$ $7 V$ and a current supply of $3 A$ $3 A$ . How long will it take for the toy car to accelerate from rest to $\frac{5}{3} \frac{m}{s}$ $5/3 m/s$ ?

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Answer 1 · 2017-04-09T06:37:11

The time is $= 0.2 s$ $=0.2s$

Voltage is $U = 7 V$ $U=7V$

Current is $I = 3 A$ $I=3A$

The power is

$P = U I = 7 \cdot 3 = 21 W$ $P=UI=7*3=21W$

Velocity is $v = \frac{5}{3} m s^{- 1}$ $v=5/3ms^-1$

Mass is $m = 3 k g$ $m=3kg$

The kinetic energy is

$K E = \frac{1}{2} m v^{2} = \frac{1}{2} \cdot 3 \cdot {(\frac{5}{3})}^{2} = \frac{25}{6} J$ $KE=1/2mv^2=1/2*3*(5/3)^2=25/6J$

But,

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

The time is $t = \frac{E}{P} = \frac{\frac{25}{6}}{21} = 0.2 s$ $t=E/P=(25/6)/21=0.2s$

An electric toy car with a mass of 3kg3 kg is powered by a motor with a voltage of 7V7 V and a current supply of 3A3 A. How long will it take for the toy car to accelerate from rest to 53ms5/3 m/s?