Introduction to Forces

A good question to start with is:

What is a Force?

And the answer is:

"A force is a push or a pull that acts on one object due to its interaction with some other object."

For example:

1) The force between a shopping trolley and a customer when the customer pushes the trolley along the aisle.

2) The force between a strong man and a car when the strong man pulls the car along a road.

3) The force felt between two magnets.

4) The force felt between a ball and the ground (the Earth) which is particularly noticeable when the ball is released from a height above the ground.

For each of the examples mentioned you should be able to identify the 2 objects that are involved and whether the force is a push or a pull.

Can you do it?

What about this example:
A tiny comet is observed in orbit, in the Oort Cloud, perhaps a billion kilometres from an observer on Earth. What force is involved and what are the two objects?

Answer: the force is gravity and the two objects are the comet and our Sun.

The point is: there are always TWO objects involved whenever a force acts, even when the distance between them is so great that it is difficult to identify both objects; and forces are just pushes or pulls!