Question

A car accelerates from rest to speed of 100 m/s in 10 seconds. If the mass of the car is 50 kg, then power developed by the engine is:

• A. 20 KW
• B. 25 KW
• C. 30 KW
• D. 35 KW

Answer 1

The correct option is B

25 KW

The change in kinetic energy of the car would be equal to the work done by the engine. Since power is work done per unit time. So, the work done and the time taken for the K.E to change would give us the power developed by the engine.
Work done $=\frac{1}{2}\times m\times v^2=\frac{1}{2}\times 50\times {100}^2=250000J$

Power $=\frac{250000}{10}=25000W=25KW$