6 In this question use \(\boldsymbol { g } = 9.8 \mathbf { m ~ s } ^ { - 2 }\) A light elastic string has natural length 3 metres and modulus of elasticity 18 newtons.
One end of the elastic string is attached to a particle of mass 0.25 kg
The other end of the elastic string is attached to a fixed point \(O\)
The particle is released from rest at a point \(A\), which is 4.5 metres vertically below \(O\) 6

1. Calculate the elastic potential energy of the string when the particle is at \(A\)
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2. The point \(B\) is 3 metres vertically below \(O\) Calculate the gravitational potential energy gained by the particle as it moves from \(A\) to \(B\)
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3. Find the speed of the particle at \(B\)
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4. The point \(C\) is 3.6 metres vertically below \(O\)
   Explain, showing any calculations that you make, why the speed of the particle is increasing the first time that the particle is at \(C\)