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3.1. Explain (i) what is meant by an inertial frame of reference, and (ii) whether the earth's motion around the sun is an inertial frame of reference or not. [5] 3.2. Why is Newton's first law used to define an inertial frame of reference? [5] 3.3. Newton's second law, and the laws of conservation of momentum and conservation of energy are all invariant under Galilean transformation. (0) Explain what is meant by the term invariant. [3] (ii) The Galilean transformations of classical mechanics are equations that describe a specific event from an inertial coordinate system relative to another inertial coordinate system. Given the equations to be: x = x' + vt ; y = y';z=z';t=ť Page 3 of 6 HPSG031 SEP/OCT EXAMINATION 2020 Show that the acceleration of a moving body is invariant under a Galilean transformation. [7] 3.4. A rocket ship flies at a speed of 0.800c over a man on earth at a time t = 0 seconds. 3.00 seconds later, the man observes an event happening from him at a distance 5.00 m. How far is this event from the astronaut in the rocket ship? What can you say about your answer? [5]