Two blocks, A and B, are on a horizontal frictionless surface. The blocks are joined together by a spring, as shown in [Figure 2.1]. Block A has mass 4.0 kg and block B has mass 6.0 kg. The variation of the tension F with the extension x of the spring is shown in [Figure 2.2]. The two blocks are held apart so that the spring has an extension of 8.0 cm.

1. (a)State the principle of conservation of momentum.[2]
2. (b)(i)Show that the elastic potential energy of the spring at an extension of 8.0 cm is 0.48 J.[2]
3. (b)(ii)1.The blocks are released from rest at the same instant. When the extension of the spring becomes zero, block A has speed vA and block B has speed vB. For the instant when the extension of the spring becomes zero, use conservation of momentum to show that kinetic energy of block A / kinetic energy of block B = 1.5[3]
4. (b)(ii)2.use the information in (b)(i) and (b)(ii)1 to determine the kinetic energy of block A. It may be assumed that the spring has negligible kinetic energy and that air resistance is negligible.[2]
5. (b)(iii)The blocks are released at time t = 0. On [Figure 2.3], sketch a graph to show how the momentum of block A varies with time t until the extension of the spring becomes zero. Numerical values of momentum and time are not required.[2]

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