The blocks shown in figure (9-E19) have equal masses. The surface of A is smooth but that of B has a friction coefficient of 0.10 with the floor. Block A is moving
at a speed of 10 m/s towards B which is kept at rest. Find the distance travelled by B if (a) the collision is perfectly elastic and (b) the collision is perfectly inelastic. Take g = 10 m/s2.


Given that B has a friction coefficient of 0.10 with the floor.


Both the blocks have equal mass m.


Block A is moving at a speed of 10 m/s (u1=10 m/s) towards B which is kept at rest (u2=0 m/s).


Let v1 and v2 are velocities of block A and B after collision.


{a} If the collision is perfectly elastic


According to conservation of momentum





_________ (1)


Again,




__________ (2)


Subtracting equation (2) from (1)




The deceleration of B is


Putting work energy principle






Where h is the distance travelled by B


{b} If the collision is perfectly inelastic


Let the final velocity of both the blocks A and B is v.


Then, according to law of conservation of momentum






The two blocks will move together sticking to each other.


Therefore, putting work energy principle






Where s is the distance travelled by B.


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