Teaching Forces

Background knowledge for teachers

NEWTON’S LAWS OF MOTION

1. An object will stay at rest, or move at a constant speed, unless acted upon by an unbalanced force.

2. The acceleration of an object acted upon by an unbalanced force is directly proportional to the magnitude of the force and inversely proportional to its mass.

3. To every action force there is an equal and opposite reaction force.

Newton’s laws can confuse learners. The following slide provides simple explanations of Newton’s Laws of Motion.

At primary it is good for children to experience and discuss the effects of forces.

All Complicated Forces Explained

1. Balanced forces cause objects to stay at rest or travel at a constant speed.

A bullet travelling through space just keepson going.

2. Unbalanced Forces cause objects to speed up or slow down.

I’d rather push a Mini than a 4X4!

3. To every Action Force there is an equal and opposite Reaction Force.

If you shove me I’ll shove you back (at the same time)!

Elicit their ideas

• Get learners to discuss what they think prior to investigating

• Use interesting, engaging activities to get them thinking/wondering

• Find out any misconceptions

• All of the above are important before learners can new construct new meaning

Common Pupil Myth

An object which does not move has no forces acting on it.

Balanced Forces

• Are there any forces acting on this cup?

Hang About!

Try strings and arrows!

Which forces are acting on

This object?With a difficult concept such as upthrust

from a table it can be useful to get learners

to think about examples they can visualise

e.g. a nail pushing up on a string, water pushing up on a boat.

Types of Forces

• Pushing Forces

• Pulling Forces

Different types of forces should be explored with learners. They need hands on opportunities to experience and investigate these and think about and discuss their ideas about everyday examples.

Buoyancy

• A few ideas for getting them talking, thinking and helping them to construct new meanings.

Lava Lamp

Dancing Raisins

Water Density

Gravity

Therefore, the Moon can’t have Gravity because it doesn’t have an atmosphere.

Learners commonly have misconceptions about gravity e.g. The Earth has gravity because it has an atmosphere.

Challenging learners’ ideas about gravity

• Ask learner’s to draw forces diagrams which show where gravity is pulling when people are at different locations on Earth

• Use tennis balls that look the same but one is injected with water to explore Galileo’s theory

• Watch videos of astronauts on the moon and discuss how and why gravity is weaker on the moon

Fun with Gravity

• Galileo

• Astro-Blaster

• Centre of Gravity

Friction – possible activities

• O-Wings

• Gripping Rice!

• Potato Spears

Air Resistance – Possible Activities

• Streamlining

• Rockets

Great Resources

• www.abc.net.au/science/surfingscientist/

• www.planet-science.com/

• Little Book of Experiments

• www.planet-science.com/experiment/