Question

A 0.246 kg toy car is powered by one D cell (1.50 V) connected directly to a small DC motor. The car has an effective energy conversion efficiency of 30.6 % , meaning that 30.6 % of the electric energy applied to the motor is converted into translational kinetic energy. After 7.88 s , the car, which is initially at rest, reaches a speed of 2.89 m / s . What is the average current supplied to the car's motor?

Answer 1

Answer:

0.284 A

Explanation:

We are given that

Mass,m=0.246 kg

Potential difference,V=1.50 V

Efficiency=30.6%

Time,t=7.88 s

Initial speed=0

Speed,v=2.89 m/s

Kinetic  energy=$K.E=\frac{1}{2}mv^2$

Using the formula

$K.E=\frac{1}{2}(0.246)(2.89)^2=1.027 J$

30.6% of Electric energy=K.E

$E=\frac{K.E\times 100}{30.6}$

$E=\frac{1.027\times 100}{30.6}=3.357 J$

$E=VIt$

$I=\frac{E}{Vt}=\frac{3.357}{1.5\times 7.88}$

$I=0.284 A$