Answer :


Mass of the heavier block, m1 = 3 kg

Mass of the lighter block, m2 = 2 kg

Let the tension in the string be T and acceleration in the system be a.

According to the diagram,

T = m1a + m1g T = 2(g+a)

m2g = T + m2a T = 3(g-a)

a= g/5 m/s2

We need to find work done by gravity in the fourth second.

Time, t = 4 s

Change in height, h = 1/2 a(2t-1) (From equations of motion)

Work done by gravity = (m2-m1)×g×h

= (3-2) × 9.8 × 6.86

= 67.228 N

≈ 67 N

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