An electric toy car with a mass of $7 k g$ $7 kg$ is powered by a motor with a voltage of $6 V$ $6 V$ and a current supply of $9 A$ $9 A$ . How long will it take for the toy car to accelerate from rest to $\frac{14}{3} \frac{m}{s}$ $14/3 m/s$ ?

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Answer 1 · 2017-12-06T06:20:09

The time is $= 0.47 s$ $=0.47s$

The power is

$P = U I$ $P=UI$

The voltage is $U = 6 V$ $U=6V$

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

The power is

$P = U I = 6 \cdot 9 = 54 W$ $P=UI=6*9=54W$

The kinetic energy of the car is

$E = \frac{1}{2} m v^{2}$ $E=1/2mv^2$

The mass is $m = 7 k g$ $m=7kg$

The speed is $v = \frac{14}{3} m s^{- 1}$ $v=14/3ms^-1$

so,

$E = \frac{1}{2} \cdot 7 \cdot {(\frac{14}{3})}^{2} = 25.28 J$ $E=1/2*7*(14/3)^2=25.28J$

Let the time $= (t) s$ $=(t)s$

$E = P t$ $E=Pt$

$t = \frac{E}{P} = \frac{25.28}{54} = 0.47 s$ $t=E/P=(25.28)/54=0.47s$

An electric toy car with a mass of 7kg7 kg is powered by a motor with a voltage of 6V6 V and a current supply of 9A9 A. How long will it take for the toy car to accelerate from rest to 143ms14/3 m/s?