4. A light elastic string \(A B\) of natural length 1.5 m has modulus of elasticity 20 N . The end \(A\) is fixed to a point on a smooth horizontal table. A small ball \(S\) of mass 0.2 kg is attached to the end \(B\). Initially \(S\) is at rest on the table with \(A B = 1.5 \mathrm {~m}\). The ball \(S\) is then projected horizontally directly away from \(A\) with a speed of \(5 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). By modelling \(S\) as a particle,

1. find the speed of \(S\) when \(A S = 2 \mathrm {~m}\). When the speed of \(S\) is \(1.5 \mathrm {~m} \mathrm {~s} ^ { - 1 }\), the string breaks.
2. Find the tension in the string immediately before the string breaks.
   (5)