What is the centripetal force that holds planets in orbit?

If we approximate the orbit of the planets around the Sun to circular orbits with a uniform circular motion, where the velocity is a vector, whose direction is perpendicular to the radius of the trajectory; the acceleration is directed towards the center of the circumference (that's why it's called centripetal acceleration).  

Now, according to Newton's 2nd law, the force is directly proportional and in the same direction as the acceleration:  

Therefore the net force resulting from the movement of a planet orbiting the Sun points towards the center of the circle, this is called Centripetal Force which is a central force that in this case is equal to the gravity force.

1 a

2 b

3 b

4 d

5 d

6 d

explanation:

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.