Question

Two blocks A and B of masses 3 m and m
respectively are connected by a massless and
inextensible string. The whole system is
suspended by a massless spring as shown in
figure. The magnitudes of acceleration of A and
B immediately after the string is cut, are
respectively:-
u​

Answer 1

Answer:

1:If block A on upper and B on lower

acceleration of A =g/3

acceleration of B=g

2:If block A on lower and B on upper

acceleration of A=g

acceleration of B=3g

Explanation:

1)For block B rope is cut tension in string is zero then

mg=ma

acceleration of B=g

For block A

spring force= all lower forces before cutting the string=Tension+weight of block A=mg+3mg=4mg

immediately after rope is cut then

spring force- weight of A=3ma

4mg-3mg= 3ma ......(mass of A=3m)

mg=3ma

acceleration of A=g/3

2)For block A

If rope is cut then

3mg=3ma

acceleration of A=g

For block B

spring force=Tension+weight of B

=3mg+mg=4mg

If rope is cut then

spring force-weight of B=mg

4mg-mg=ma

3mg=ma

acceleration of B=3g