Discuss the below:
Q: An object moving to the right at 0.8c is struck head-on by a photon of wavelength lambda, moving to the left. The object absorbs the photon (i.e. the photon disappears) and is afterward moving to the right at 0.6c.
(a) Determine the ratio of the object's mass after the collision to its mass before the collision.
(b) Does kinetic energy increase or decrease?