An electric toy car with a mass of $3 k g$ $3 kg$ is powered by a motor with a voltage of $9 V$ $9 V$ and a current supply of $5 A$ $5 A$ . How long will it take for the toy car to accelerate from rest to $\frac{5}{2} \frac{m}{s}$ $5/2 m/s$ ?

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Answer 1 · 2017-04-27T15:59:36

The time is $= 0.21 s$ $=0.21s$

Voltage is $U = 9 V$ $U=9V$

Current is $I = 5 A$ $I=5A$

The poweris

$P = U I = 9 \cdot 5 = 45 W$ $P=UI=9*5=45W$

Velocity is $v = \frac{3}{2} m s^{- 1}$ $v=3/2ms^-1$

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

The kinetic energy is

$K E = \frac{1}{2} m v^{2} = \frac{1}{2} \cdot 3 \cdot {(\frac{5}{2})}^{2} = \frac{75}{8} J$ $KE=1/2mv^2=1/2*3*(5/2)^2=75/8J$

But,

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

The time is $t = \frac{E}{P} = \frac{\frac{75}{8}}{45} = 0.21 s$ $t=E/P=(75/8)/45=0.21s$

An electric toy car with a mass of 3kg3 kg is powered by a motor with a voltage of 9V9 V and a current supply of 5A5 A. How long will it take for the toy car to accelerate from rest to 52ms5/2 m/s?