Q. The energy required to accelerate a car from $10\ m/s$ to $20\ m/s$ is how many times the energy required to accelerate the car from rest to $10\ m/s$
A) Equal
B) 4 times
C) 2 times
D) 3 times
Explanation
(d) Kinetic energy for first condition
$= \frac{1}{2}m\left( v_{2}^{2} - v_{1}^{2} \right) = \frac{1}{2}m\left( 20^{2} - 10^{2} \right) = 150\ mJ$
K.E. for second condition $= \frac{1}{2}m\left( 10^{2} - 0^{2} \right) = 50mJ$
$\therefore\frac{(K.E.)I}{(K.E.)II} = \frac{150m}{50m} = 3$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.