Download Aptitude Crack
img not found img not found

UPSC Civil Service Exam Questions - Engineering

Q1:

Two spheres of mass 15 kg and 20 kg, move along a straight line in the same direction with velocities of 20 m/s and 5 m/s, respectively. If the coefficient of restitution is 0.7, then the velocity of the 15 kg mass after collision will be

A 5.43 m/s

B 15.93 m/s

C 18.72 m/s

D 16.16 m/s

ANS:A - 5.43 m/s

Accoring to law of conservation m1u1+m2u2 = m1v1+m2v2.
Then 15v1+20v2=15*20+20*5 or 3v1+4v2 = 80.
Another eqn from co efficient of restitution v2-v1 = e(u1-u2) or v2-v1=0.7(20-5)=10.5 Or v2-v1=10.5.

Solving two eqn v1=5.43 & v2=15.93 m/s.