Back to P5 Home
P5 B) Contact & Non-Contact Forces
P5 B) Contact & Non-Contact Forces
There are two different types of forces; contact and non-contact forces. Contact forces are forces between two objects that are physically touching one another. Non-contact forces are forces between two objects that are not physically touching one another. Also, forces can either be pushing forces or pulling forces.
Contact Forces
Contact forces are forces between two objects that are physically touching one another; the objects are in contact with each other. A few examples of contact forces are air resistance, the normal reaction force, friction and tension. We are going to look at each of these contact forces in more detail.
Air Resistance
An object that is moving through air will experience air resistance. The air resistance force is in the opposite direction to the direction of travel. For example, when a skydiver has jumped out of a plane, the direction of travel for the skydiver is downwards and air resistance is upwards (the opposite direction to the direction of travel).
Contact forces are forces between two objects that are physically touching one another; the objects are in contact with each other. A few examples of contact forces are air resistance, the normal reaction force, friction and tension. We are going to look at each of these contact forces in more detail.
Air Resistance
An object that is moving through air will experience air resistance. The air resistance force is in the opposite direction to the direction of travel. For example, when a skydiver has jumped out of a plane, the direction of travel for the skydiver is downwards and air resistance is upwards (the opposite direction to the direction of travel).
Friction
When one object is sliding past another object, the objects will experience friction. The frictional force will be in the opposite direction to the object’s direction of travel. For example, if you pushed a box towards the right, the frictional force would be towards the left (the opposite direction to the direction of travel).
When one object is sliding past another object, the objects will experience friction. The frictional force will be in the opposite direction to the object’s direction of travel. For example, if you pushed a box towards the right, the frictional force would be towards the left (the opposite direction to the direction of travel).
Normal Reaction Force
When we place an object on a surface, the surface will exert an equal and opposite force on the object (this force is known as the normal reaction force). The normal reaction force is why the object does not fall through the surface. For example, let’s suppose that we place a cup onto a table. Weight is the force pulling the object towards the earth (downwards). The table exerts a normal reaction force that is equal and opposite to the weight of the object (the normal reaction force is upwards). The normal reaction force is why the cup stays on the top of the table and does not go through the table. There is a diagram of this taking place below.
When we place an object on a surface, the surface will exert an equal and opposite force on the object (this force is known as the normal reaction force). The normal reaction force is why the object does not fall through the surface. For example, let’s suppose that we place a cup onto a table. Weight is the force pulling the object towards the earth (downwards). The table exerts a normal reaction force that is equal and opposite to the weight of the object (the normal reaction force is upwards). The normal reaction force is why the cup stays on the top of the table and does not go through the table. There is a diagram of this taking place below.
Tension
An object that is being stretched will experience tension. Tension is a pulling force that can occur in a rope, cable, chain etc. Let’s look at the tension for a lamp hanging from a ceiling by a cable. Weight is the force that is pulling the lamp shade towards the earth (downwards). Tension in the cable is pulling the lampshade upwards.
An object that is being stretched will experience tension. Tension is a pulling force that can occur in a rope, cable, chain etc. Let’s look at the tension for a lamp hanging from a ceiling by a cable. Weight is the force that is pulling the lamp shade towards the earth (downwards). Tension in the cable is pulling the lampshade upwards.
Non-Contact Forces
Non-contact forces are forces between two objects that are not physically touching one another. A few examples of non-contact forces are magnetic forces, gravity and electrostatic forces. We are going to look at each of these non-contact forces in more detail.
Magnetism
A magnetic force is experienced by any magnetic material in a magnetic field. There are two different types of magnetic forces; attraction and repulsion. Magnets have two different poles; a north and a south pole.
Opposite magnetic poles attract one another. This attractive force can come from a north-south or a south-north.
Non-contact forces are forces between two objects that are not physically touching one another. A few examples of non-contact forces are magnetic forces, gravity and electrostatic forces. We are going to look at each of these non-contact forces in more detail.
Magnetism
A magnetic force is experienced by any magnetic material in a magnetic field. There are two different types of magnetic forces; attraction and repulsion. Magnets have two different poles; a north and a south pole.
Opposite magnetic poles attract one another. This attractive force can come from a north-south or a south-north.
Like magnetic poles repel one another. This repulsive force can come from north-north or south-south.
Electrostatic Forces
A charged particle/ object in an electric field will experience an electrostatic force. This electrostatic force can be attraction or repulsion.
Opposite charges attract one another; positive and negative charges will attract each other.
Like charges repel one another; this happens when we have positive-positive or negative-negative.
Gravity
Masses are attracted to each other by gravitational forces. An example of a gravitational force is the attraction between the sun and the earth. Both the sun and the earth experience an equal and opposite force of attraction.
Weight is a non-contact force that is caused by gravity.