The relation between the magnitudes of acceleration of pulley P1 (ap1) and that of pulley P3 (ap3) is
=
∴ x1 + x1 - x2 + x3 - x2 + x3 - x1 = L
L is length of string.
⇒ x1 - 2x2 + 2x3 = L
Assuming mass 'm' moves downward
P1 will move up. Which means distance from P1 and reference point will reduce.
∴d2x1dt2=−a(p1)
Differentiating twice
∴ ⇒ - a1 - 0 + 2a3 = 0 (x2 is constant)
⇒ 2 a3 = a1
⇒ 2a(p3) = a(p1)