Non-Contact Forces – Lesson Summary

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Learning Objective

In this lesson we will learn about three types of non-contact forces – gravity, magnetism and electrostatic forces.

Learning Outcomes

By the end of this lesson you will be able to:

  • Explain what gravity is and describe how it affects the motion of objects.
  • Discuss how gravitational force is related to mass and distance.
  • Differentiate between mass and weight.
  • Calculate the weight of an object.
  • Explain what magnetism is and describe how it affects certain metals.
  • Describe the different types of interactions between two magnets.
  • Describe Earth’s geomagnetic field.
  • Explain what electrostatic forces are and describe the different types of interactions between charged particles.
  • Describe static electricity, with examples.

 
non-contact forces gravity magnetism electrostatic forces lesson contents

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Lesson Topics

1 | Gravitational Force

2 | Gravity on Earth

3 | Gravity in the Solar System

4 | Mass and Weight

5 | Gravity and Distance

6 | Magnetic Force

7 | Magnetic Fields

8 | Earth’s Magnetic Field

9 | Electrostatic Forces

10 | Static Electricity

11 | Summary

Lesson Summary

  • Gravity (gravitational force) is a non-contact force of attraction between any two objects.
  • The magnitude of the gravitational force between two objects depends on their masses and the distance between them.
  • The greater the masses, the greater the gravitational force.
  • The greater the distance, the less the gravitational force.
  • Gravity prevents objects from flying off into space as the Earth rotates on its axis, and causes unsupported objects to accelerate towards the ground.
  • On Earth, the rate of acceleration due to gravity (gravitational acceleration) is about 10 m/s2 for all objects, regardless of their mass.
  • Gravity also causes celestial objects, such as moons, to orbit larger celestial objects, such as planets.
  • Tides on Earth are caused by the moon’s gravitational pull as it orbits Earth.
  • Weight is a force acting on an object due to gravity.
  • It is measured in Newtons (N).
  • The weight of an object is proportional to the object’s mass (the amount of matter in the object) as well as gravity, as shown by the following formula:
  • calculating weight from mass and gravity formula summary
  • Magnetism (magnetic force) is a non-contact force of attraction or repulsion between a magnet and a metal or between two magnets.
  • A magnet is an object that produces a magnetic field, which consists of invisible magnetic field lines radiating outwards from the two poles.
  • Certain metals, such as iron, nickel and cobalt, are attracted to magnets.
  • When two magnets interact:
  • Unlike poles will attract each other.
  • Like poles will repel each other.
  • The Earth has its own magnetic field, called the geomagnetic field.
  • The Earth’s magnetic poles are slightly tilted with respect to Earth’s geographic poles.
  • A compass is a navigational device containing a magnetic needle that aligns itself with Earth’s geomagnetic field.
  • Electrostatic forces are non-contact forces of attraction or repulsion between electrically charged particles.
  • Unlike electric charges will attract each other.
  • Like electric charges will repel each other.
  • Static electricity is the build-up of electric charge on the surface of a substance as a result of friction.

 
compass needle north

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