Occurrence of a day and night

Roration or Revolution​

A2 kg ball travellng to the right with a speed of 4 m/s collidees with a 5 kg ball traveling to the left with a speed of 3 m/s. take right to be the positive direction. what is the total momentum of the two balls before they collide? what is the total momentum of the two balls after they collide?

How can waves travel through ground?

Convection currents are caused by differences in what two things?