Recitation week 11 conservation of momentum some Useful Relationships

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    1. Some Useful Relationships. The following relationships between the momentum and kinetic energy of an object can be very useful for calculations: If an object of mass m has momentum of magnitude p and kinetic energy K, show that (a) K=(p2 /2m), and (b) p=sqroot(2mk) (c) Find the momentum of a 1.15 kg ball that has 15.0 J of kinetic energy. (d) Find the kinetic energy of a 3.50 kg cat that has 0.220kg.m/s of momentum.

8-13 On a frictionless, horizontal air table, puck A (with mass 0.250kg) is moving toward puck B (with mass 0.350 kg), which is initially at rest. After the collision, puck A has a velocity of 0.120m/s to the left, and puck B has a velocity of 0.650 m/s to the right. (a) What was the speed of puck A before the collision? (b) Calculate the change in the total kinetic energy of the system that occurs during the collision?

    1. Block A in the figure has mass 1.00kg, and block B has mass 3.00kg. The blocks are forced together, compressing a spring S between them; then the system is released from rest on a level, frictionless surface. The spring, which has negligible mass, is not fastened to either block and drops to the surface after it has expended. Block B acquires a speed of 1.20 m/s. (a) What is the final speed of block A?

(b) How much potential energy was stored in the compressed spring?

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