What principle makes radio telescopes better than single dish telescopes

Describe how the fermi level changes with donor level, temperature and contact with p and n type semiconductors

Mutt and jeff are running along a path each pushing a cart loaded with rocks. if mutt's wagon has a mass two times greater than jeff's and they want to stay together, arriving at their destination at the same time, what must happen? a) jeff should slow down so mutt can catch up. b) mutt must use half as much force to push his cart. c) mutt must use twice as much force to push his cart. d) mutt and jeff will use the same force, but mutt will take bigger steps.

What object a collides with object b and bounces back its final momentum is?