A light elastic string has natural length 5 m and modulus of elasticity 20 N . The ends of the string are attached to two fixed points \(A\) and \(B\), which are 6 m apart on a horizontal ceiling. A particle \(P\) is attached to the midpoint of the string and hangs in equilibrium at a point which is 4 m below \(A B\).
Calculate the weight of \(P\).
The particle is now raised to the midpoint of \(A B\) and released from rest.
Calculate the speed of \(P\) when it has fallen 4 m .