Problem: An astronomer is investigating the possibility of sending a satellite to Ganymede, a moon of Jupiter.
The plan is to use a rocket to launch the satellite into space above the Earth and then for the satellite to deploy a solar sail to carry it out towards Ganymede. A solar sail is a large mirror which is pressed on by photons, particles of light, emitted by the sun thereby generating a small force.
a. The planned satellite would have a mass of 56.5 kg. When first deployed, the solar sail is expected to generate a propulsive force of 3.5 N.
i. What would be the initial acceleration of the satellite? Give your answer to an appropriate number of significant figures and in scientific notation.
ii. Assuming that the satellite starts from rest and the acceleration remains constant, how long would it take for the satellite to reach a speed of 100 km s-1? Give your answer to the nearest week.
iii. How would you expect the force on the solar sail to change, if at all, as the satellite moves away from the Sun and towards Ganymede? Explain your answer.
iv. A colleague suggests changing the reflectivity of the mirrored surface of the solar sail so that it absorbs less light and reflects more light backwards. Explain how this change would affect the force generated by the solar sail.
When the satellite reaches Ganymede, the plan is to send a small capsule down to the moon's surface.
b.
i. In no more than two sentences, explain the difference between the capsule's mass and its weight.
ii. On Earth the capsule weighs 84 N. How much will the capsule weigh on Ganymede where the acceleration due to gravity is 1.428 m s-2?
If required, you should take the acceleration due to gravity on Earth to be 9.8 m s-2. Give your answer to an appropriate number of significant figures.
iii. As the capsule descends to the surface of Ganymede, thrusters are used to provide an upward force. If the capsule descends at a constant velocity, how much upwards force is provided by the thrusters? Ganymede does not have an atmosphere.