Will give Brainliest What is the focal length of a mirror that has a radius of curvature of 0.10 m?

I'd appreciate if you also explained how you got this or worked it out thanks.​

A1200 kg car traveling north at 10 m/s is rear-ended by a 2000 kg truck traveling at 30 m/s. what is the total momentum before and after the collision?

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground.what is his gravitational potential energy above the ground?