Newton’s Third Law (with free body diagrams in 2D)
I can draw force diagrams and identify pairs of forces that obey Newton’s Third Law.
Newton’s Third Law (with free body diagrams in 2D)
I can draw force diagrams and identify pairs of forces that obey Newton’s Third Law.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- Some forces require contact between objects, while others do not.
- Forces are vectors and can be drawn as arrows on diagrams.
- A free body diagram shows all of the forces acting on a single object.
- For every force there is an equal sized force acting in the opposite direction.
- Force pairs have the same magnitude and type, and act in opposite directions between two objects.
Keywords
Non-contact force - A force that exists between objects, even if they are not touching.
Contact force - A force that exists between objects when they are touching.
Normal contact force - The overall effect of a set of forces acting on an object is represented by a single resultant force.
Free body diagram - A diagram showing all of the forces acting on a single object.
Newton’s third law - Forces come in equal and opposite pairs, which act on pairs of different objects.
Common misconception
Pupils may regard force as a property of an object, expressing ideas such as ‘the object has a force’ and ‘the object runs out of force’.
Describe forces as interactions between two objects, using the phrasing ‘the force of object A on object B’.
Equipment
None required.
Licence
Lesson video
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Starter quiz
6 Questions
Exit quiz
6 Questions
one force representing the overall effect of all forces on an object
a force that exists between objects only when they are touching
a force that exists between objects even if they are not touching
