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UPSC Civil Service Exam Questions - Engineering

Q1:

A car accelerates from rest to a speed of 10 m/s and the energy spent in doing this is E. If the car is further accelerated from 10 m/s to 20m/s, what is the amount of energy to be spent further ?

A E

B 2E

C 3E

D 4E

ANS:D - 4E

According to the Equation, KE=(1/2)mv^2.
The energy required to accelerate the car to 10m/s (given 'E').
Therefore mass=2E/100.
Energy required to accelerate to 20m/s=(1/2)*(2E/100)*20*20=4E.
Energy required to accelerate from 10m/s to 20m/s = 4E-1E=3E.
Therefore it is equal to 3 times the initial energy required.