Question

Match the block diagrams of block of mass 'm' with their corresponding free body diagram. (String is massless)

• A. P - (iii); Q - (ii); R - (v); S - (vi)
• B. P - (ii); Q - (iii); R - (vi); S - (v)
• C. P - (i); Q - (ii); R - (v); S - (iii)
• D. P - (ii); Q - (iii); R - (vi); S - (iv)

Answer 1

The correct option is B

P - (ii); Q - (iii); R - (vi); S - (v)

P - (ii)

Block m will be pulled by earth's gravity in downward direction and the force will be mg.

String is being pulled by block and also it is tied to the ceiling so it's tight and will have Tension; and it will pull the block upwards with Tension T.

Q - (iii)

Again mg is obviously due to earth. The lower block pulls the upper block and hence the string will be tight and have tension (let's say $T_2$) and will pull the block with that tension.

Similarly upper string will have tension $T_1\left(le{t}^{\prime }ssay\right)$

R — (vi)

The string is not tight as there is no force pulling the string rightwards. So there will be no tension in the string. Normal is obviously by ground.

S— (v)

Here string is tight as the lower block pulls it down.' Mg' by gravity of Earth and normal by the ground which balances gravitational pull.