Q.6 The proper length of a rod is 10m. Calculate the length of the rod when it is moving with a velocity of 3000 km/s. What will be the change in length of the rod when it is moving with the velocity of (a) 3km/hr., (b) 0.99c. Q.7 Muon-particles are created at an altitude of more than 6000 m by cosmic rays coming from the outer space. These particles have an average life of 2 x 10-6 s in their rest frame and travel towards the earth with a typical speed of 2.994 x 108 m/s. Evaluate the lifetime of muons as measured by an observer on earth. Also find the distance travelled by the muon as measured by the same observer. Solve the problem of muon lifetime from its rest frame of reference.