A spear is thrown by you at a very high speed.As it passes,you measure its length at 1/2 its normal length.From this you conclude that the moving spear's mass must be
A) one-half its rest mass.
B) twice its rest mass.
C) four times its rest mass.
D) None of these choices are correct.

Question

Quizplus · Accepted Answer

According to the theory of relativity, as an object's speed approaches the speed of light, its relativistic mass increases. The length contraction observed indicates high speed, which implies the relativistic mass is greater than the rest mass. Specifically, the relativistic mass is given by the rest mass multiplied by the Lorentz factor, which is greater than 1, making it twice the rest mass in this scenario.

A Spear Is Thrown by You at a Very High