To an object thrown up into the air, gravity is an

1.   ?    Internal force
2.   ?    External force

A mother pushes her child on a swing. The mother's push in relation to just the baby.

1.   ?    Internal force
2.   ?    External force

Two people push off of each other.

1.   ?    Internal force
2.   ?    External force

The forces in a collision

1.   ?    Internal forces
2.   ?    External forces

A person walking in a row boat. The force of the foot on the boat is an

1.   ?    Internal force
2.   ?    External force

A mother pushes her child on a swing. The mother's push in relation to the mother and the baby is an

1.   ?    Internal force
2.   ?    External force

Friction (always)

1.   ?    Internal force
2.   ?    External force

An explosion to the pieces of the bomb afterward.

1.   ?    Internal force
2.   ?    External force