Forces can be divided into contact and non-contact. When force is applied, it can alter an object’s direction of movement, speed and shape.
A contact force is a force that requires contact to act on an object.
Below are examples of contact forces:
Also known as a normal contact force, a reaction force is a force which is exerted in the opposite reaction to an action force. ‘An equal and opposite force‘
For example, a book on a table experiences a reaction force.
The book on the table is exerting a downward force on the table, while the table is exerting an upward reaction force on the book. These forces are equal and opposite, so the book remains at rest.
Tension is a pulling force that stretches an object. For example, in tug of war, two people or groups pull the rope in opposite directions.
Friction is the resistance of motion when two objects slide over each other.
An example of this is when skateboarding.
There will be friction between the wheels of the skateboard and the ground.
A force of friction that takes place between air and another object.
An example of air resistance is with a moving car.
When a car moves, the air surrounding it forms a resistance in the opposite direction to the movement of the car.
A non-contact force is a force that acts on an object without physically touching it. There are many types of non-contact forces. Three examples are:
We can also describe non-contact forces as fields of influence around an object.
Magnetic forces are forces that can attract or repel other magnetic materials in a magnetic field.
Gravity is a force that attracts all objects with mass towards each other. This becomes very noticeable when dealing with large bodies of mass, such as planets, this is because the greater the object’s mass is, the greater the gravitational force. Gravitational force pulls inwards, towards the object’s centre. This is why on Earth we are pulled towards the ground.
Electrostatic forces are forces between two objects that are charged.