Net pulling force = 2g - 1g = 10 N Mass being pulled = 2 + 1 = 3 kg ∴ Acceleration of the system is a =
10
3
m∕s2 ∴ Velocity of both the blocks at t =1 s will be v0=at=(
10
3
)(1)=
10
3
m∕s Now at this moment, velocity of 2kg becomes zero, while that of 1kg block is 10m∕s upwards. Hence, string becomes tight again when displacement of 1kg block = displacement of 2kg block. ⇒v0t−