1. (10 marks) Meson is a kind of unstable particle with lifetime about 2.6 x 10'8s. (a) If it travels with speed 0.80, how long in time will it decay in the laboratory frame? (b) How long in length will it move in the laboratory frame? 2. (20 marks) A rod with rest length In is moving along its length relative to the laboratory with a speed a. A particle is moving with the same speed in the opposite direction. How long does it take for the particle to pass the rod in (a) the rest frame of the rod? (b) the laboratory frame? (0) the rest frame of the particle? 3. (20 marks) A train of proper length la is moving with speed '1) relative to the ground. A ball moves from the back of the train with speed a relative to the train. Find out the time taken for the ball to move from the back to the front of the train as measured by an observer on the ground