A force is a push or pull. Forces are needed to make things move. They can also make things speed up, slow down, or stop moving. Forces can also cause things to change direction or change shape. Most forces only act when things touch each other. Other forces, such as gravity and magnetism, act at a distance.
Pushing forces
A sail boat uses the pushing force of the wind to start moving and to keep moving in the water. If the wind dies down, the boat will slow down and eventually stop, because the air and water are pushing back against it.
Wind
The wind pushes against the sail, moving the boat forwards through the water.
Air resistance
As the boat moves forwards, the air pushes back against it. This is called air resistance. You can feel the force of air resistance on your face when you pedal hard on a bicycle.
Water resistance
As the boat moves forwards, the water pushes back against it. You can feel the force of water resistance when you try to run through water.
Pulling forces
A small tugboat is able to pull a much larger ship through water because it has a very powerful engine. The engine produces a strong pulling force, which acts through the towline connecting the two boats.
Picture Credit : Google
