A particle of mass M is moving in a horizontal circle of radius R with uniform speed v. When it moves from one point to a diametrically opposite point, its?
A.
Kinetic energy changes by (Mv)2/4
B.
Momentum does not change
C.
Momentum changes by 2Mv
D.
Kinetic energy changes by (Mv)2
Answer: Option C
Explanation:
At any two diametrically opposite points, velocities of the particle have the same magnitude but opposite directions. Therefore change in momentum = Mv-(-MV)=2Mv.
Two identical balls A and B collide head on elastically. If velocities of A and B, before the collision are +0.5m/s and -0.3m/s respectively, then the velocities after the collision, are?
A.
-0.5m/s and +0.3m/s
B.
+0.5m/s and +0.3m/s
C.
+0.3m/s and -0.5m/s
D.
-0.3m/s and +0.5m/s
Answer: Option D
Explanation:
In an elastic collision between two bodies of equal masses, velocities get exchanges after collision. vA=-0.3m/s and vB=+0.5m/s.
