1) In one scene of the movie Raiders of the Lost Ark, Indiana Jones is running along the top of a moving train. He is running at a speed of 10 km/h, relative to the train. The train is moving at a speed of 100 km/h, relative to the ground. Draw a rough sketch of this scene. Show the position and velocity of three observers who see Indiana Jones running at each speed below.

Question

a) 10 km/h b) 20 km/h c) 110 km/h

2)The lifetime of a kaon particle, measured at rest in a laboratory, is 1.2 x 10-8 s. At what speed must the kaon particle travel to have its lifetime measured as 2.0 x 10-8 s?

Answer 1

a) Stationary observer on the train:
As the observer himself is having speed that of the train, Indiana Jones would appear to be running at 10 km/h.

b) An observer on the train running in opp. direct to the train at speed of 10km/h:
Relative to such an observer, speed of Indiana Jones would be 10+10=20Km/h.

c) an observer standing on the ground would see him running at 100+10 = 110Km/h
Draw the sketch based on above explanation.