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An experimenter measures the length of a rod. Initially the experimenter and the rod are at rest with respect to the lab. Consider the following statements.
(A) If the rod starts moving parallel to its length but the observer stays at rest, the measured length will be reduced.
(B) If the rod stays at rest but the observer starts moving parallel to the measured length of the rod, the length will be reduced.
A suitcase kept on a shop’s rack is measured 50 cm × 25 cm × 10 cm by the shop’s owner. A traveler takes this suitcase in a train moving with velocity 0.6c. If the suitcase is placed with its length along the train’s velocity, find the dimensions measured by
(a) the traveler and
(b) a ground observer
A person travels on a spaceship moving at a speed of 5c/13.
(a) Find the time interval calculated by him between the consecutive birthday celebrations of his friend on the earth.
(b) Find the time interval calculated by the friend on the earth between the consecutive birthday celebrations of the traveler.
The energy from the sun reaches just outside the earth’s atmosphere at a rate of 1400 W m–2. The distance between the sun and the earth is 1.5 × 1011 m.
(a) Calculate the rate at which the sun is losing its mass.
(b) How long will the sun last assuming a constant decay at this rate? The present mass of the sun is 2 × 1030 kg.