An electric toy car with a mass of $3 k g$ $3 kg$ is powered by a motor with a voltage of $3 V$ $3 V$ and a current supply of $7 A$ $7 A$ . How long will it take for the toy car to accelerate from rest to $4 \frac{m}{s}$ $4 m/s$ ?

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Answer 1 · 2018-04-13T16:27:17

The time is $= 1.14 s$ $=1.14s$

The power is

$P = U I$ $P=UI$

$Power = Voltage \times Current$ $"Power"="Voltage"xx"Current"$

The voltage is $U = 3 V$ $U=3V$

The current is $I = 7 A$ $I=7A$

The power is

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

The kinetic energy of the car is

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

The mass of the car is $m = 3 k g$ $m=3kg$

The speed is $v = 4 m s^{- 1}$ $v=4ms^-1$

So,

The kinetic energy is

$E = \frac{1}{2} m v^{2} = \frac{1}{2} \cdot 3 \cdot {(4)}^{2} = 24 J$ $E=1/2mv^2=1/2*3*(4)^2=24J$

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

$E = P t$ $E=Pt$

$Energy=Power \times time$ $"Energy=Power" xx "time"$

The time is

$t = \frac{E}{P} = \frac{24}{21} = 1.14 s$ $t=E/P=(24)/21=1.14s$

An electric toy car with a mass of 3kg3 kg is powered by a motor with a voltage of 3V3 V and a current supply of 7A7 A. How long will it take for the toy car to accelerate from rest to 4ms4 m/s?