1.

A small block B rests over a long block A of length L as shown figure. They aregiven sharp impulse such that they acquires speed u and v(u > v) The time takenby the block B to drop down is​

Answer»

Answer:

As there are no external forces acting on the 'A + B' system, its total momentum is conserved. If the MASSES of A and B are 2m and 2 respectively, and v is the final common velocity, MU=(m+2m)v or v=u/3

Work done against friction = loss in KE =

2

1

mu

2

−

2

1

(3m)v

2

=

2

1

mu

2

−

2

1

(3m)

9

u

2

=

2

1

mu

2

[1−

3

1

]=

3

2

×

2

1

mu

2

The FORCE of friction between the blocks is μmg.

Acceleration of A (to the right) =a

1

=

2m

μmg

=

2

μg

Acceleration of B (to the left) =a

2

=

m

μmg

=μg

Acceleration of A relative to B =a

1

−(−a

2

)=

2

3

μg.


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