Albert Teen YOU ARE LEARNING:  Non-Contact Forces  # Non-Contact Forces ### Non-Contact Forces

We will discover what a non-contact force is, and some of its examples in the real world.

Which of the following is an example of a non-contact force? A non-contact force can act over a distance so that objects do not have to be touching for the force to act. Non-contact forces can cause an effect within an area known as a field of force . Magnetism is an example of a non-contact force.

Magnetism is a non-contact force because magnetic materials have a field of force surrounding them. What is a magnetic field? A magnetic force acts on a paperclip from a nearby magnet. If the distance between them is increased, how might the magnetic force change? An electrostatic force is a non-contact force which is experienced by charged particles in an electric field, causing them to attract or repel each other. What would be the effect of an electrostatic force between two positively charged objects? To understand electrostatic charge, it is important to remember that all objects are made up of atoms. The nucleus of an atom consists of protons and neutrons, and electrons orbit the nucleus. Protons have a positive charge, electrons a negative charge, and neutrons are neutral.

If protons have a positive charge and electrons have a negative charge, an object with an overall negative charge has more of which subatomic particle? A particle becomes charged if it loses or gains electrons. Because an electron has a negative charge, the loss of an electron results in a positively charged particle, whereas the gaining of an electron results in a negatively charged particle.

If you were to rub a balloon against your jumper, friction causes electrons to be transferred from the jumper to the balloon so that the jumper has a positive charge and the balloon a negative charge. What effect does this have? The strength of an electrostatic force depends on two factors. Try to guess what these factors are! Do you think gravitational force is a contact or non-contact force? If you drop a ball it falls to the ground because of Earth's gravitational force pulling everything down towards the centre of the Earth. Gravitational forces attract any objects with mass to each other, and they are non-contact forces.

The Earth and the moon have a very strong gravitational force between them, but a pen and pencil have a very weak gravitational force between them. What does that tell us about the relationship between mass and gravitational force? A gravitational force exists between all objects with mass, but in small objects the force would be so weak that it would be unnoticeable!

Think about what you already know about non-contact forces and their field of force. Which factor other than mass will affect the strength of the gravitational force between objects? 