A spherical container is used to carry measuring instruments to the bottom of a lake. Fig. 2.1 shows the container held at rest just below the water surface of a lake. [Figure 2.1] The container is released and falls through the water to the bottom of the lake.

1. (a)The container reaches terminal velocity before it hits the bottom of the lake. Explain, in terms of the forces on the container, the motion of the container through the water until it reaches terminal velocity.[3]
2. (b)(i)The container falls through a vertical distance of 32 m before it hits the bottom of the lake. The container and instruments have a total mass of 74 kg. Calculate the energy transferred from the gravitational potential energy store of the container.[2]
3. (b)(ii)State the principle of conservation of energy.[2]
4. (b)(iii)Work is done to transfer energy from the gravitational potential energy store as the container falls at terminal velocity. Describe, in terms of the work done, how the energy is transferred from the gravitational potential energy store to one other energy store in the water.[2]

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