Concept:Since the surface is frictionless and the string is inextensible, all blocks move together with the same common acceleration under the applied force
F.
Explanation:Let the common acceleration of the system be
a.
The total mass of all three blocks is:
2 kg+8 kg+12 kg=22 kgUsing Newton's second law for the entire system:
a=22FNow, tension
T1 pulls the two blocks on its left, whose combined mass is
2+8=10 kg.
Applying Newton's second law to these two blocks:
T1=10aNext, tension
T2 pulls only the
2 kg block.
Applying Newton's second law to the
2 kg block:
T2=2aDividing the two equations:
T2T1=2a10a=15Therefore, the required ratio is
T1:T2=5:1.
Answer:T1:T2=5:1, so the correct option is B.