AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER
Scalars, vectors and forces
Forces · Lesson 1 of 20
Teacher copy - includes the notes for whoever is teaching from it.
Warm-up
Answer each one, then check.
1. What is a force?
A push or a pull
2. What is the unit of force?
The newton (N)
3. Give an example of a quantity with direction.
Velocity
4. What is friction?
A force that opposes motion between surfaces
5. What does a longer arrow mean on a force diagram?
A bigger force
Learning Objectives
1. Distinguish scalar quantities from vector quantities.
2. Represent a vector using an arrow.
3. Describe contact and non-contact forces with examples.
4. Describe the interaction between pairs of objects that produce a force on each object.
Scalars And Vectors
Scalar quantities have magnitude only. Vector quantities have magnitude and direction.
A vector is drawn as an arrow: the length shows the magnitude and the arrowhead shows the direction. Force is a vector quantity.
Forces as Vectors
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The longer the arrow, the larger the force. |
A book on a table with weight and normal contact force arrows, and a box pulled with a larger pull than the friction.
Scalar or Vector?
Learn which is which.
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Scalar (size only) |
Vector (size and direction) |
|---|---|
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Distance |
Displacement |
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Speed |
Velocity |
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Mass |
Force and weight |
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Energy, time, temperature |
Acceleration and momentum |
Contact or Non-contact?
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CONTACT FORCES (OBJECTS TOUCHING) |
NON-CONTACT FORCES (OBJECTS SEPARATED) |
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▸ Friction. ▸ Air resistance. ▸ Tension. ▸ Normal contact force. |
▸ Gravitational force. ▸ Electrostatic force. ▸ Magnetic force. |
Drawing a Force Vector
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Draw an arrow to represent a force of 6 N to the right. Use a scale of 1 cm = 2 N. |
1. Length
6 ÷ 2 = 3 cm
2. Direction
An arrowhead pointing right
Answer: A 3 cm arrow pointing to the right.
Interaction Pairs
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Two magnets are brought close together with their north poles facing. Describe the forces. |
1. Force on each magnet
Each magnet exerts a force on the other
2. Direction
Like poles repel, so each force points away from the other magnet
3. Type
Non-contact, because the magnets are not touching
Answer: Each magnet pushes the other away: equal and opposite non-contact forces.
Key Points
Use the right words.
▸ Force is a vector. It has a size in newtons and a direction.
▸ Pairs of forces. When two objects interact, each exerts a force on the other.
▸ Scale. Choose a scale so the arrows fit on the page.
▸ Examples. Name the force and its direction: 'friction to the left'.
Key Terms
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Scalar A quantity with magnitude only. |
Vector A quantity with magnitude and direction. |
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Contact force A force between objects that are touching. |
Non-contact force A force between objects that are separated. |
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Magnitude The size of a quantity. |
Newton The unit of force. |
Your Task: Sort Them
8 minutes
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Sort into scalar and vector: mass, velocity, distance, acceleration, time, force. Then say whether each of these forces is contact or non-contact: friction, gravity, magnetic force, tension. 1. Does it have direction? 2. Are the objects touching? |
A good answer shows: Scalars: mass, distance, time. Vectors: velocity, acceleration, force. Contact: friction, tension. Non-contact: gravity, magnetic force.
Note: Ask why speed is a scalar but velocity is a vector.
Can I...?
☐ Define scalar and vector.
☐ Give examples of each.
☐ Draw a vector arrow to scale.
☐ List contact forces.
☐ List non-contact forces.
☐ Describe an interaction pair.
☐ Use the word magnitude.
☐ Write force directions.
Summary
✓ Scalar: magnitude only. Vector: magnitude and direction.
✓ Force is a vector.
✓ Contact: friction, tension, air resistance, normal contact force.
✓ Non-contact: gravity, electrostatic, magnetic.
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EXAM FOCUS State whether velocity is a scalar or a vector quantity. (1 mark) Vector: it has direction. |
Exam Practice: Scalars, vectors and forces
Answer all questions. Use the mark allocation as a guide to how much to write. · 13 minutes
▸ Question 1 · 2 marks · State. Give one example of a scalar quantity and one example of a vector quantity.
▸ Question 2 · 3 marks · Complete. Some forces are contact forces and some are non-contact forces. Give one example of each.
▸ Question 3 · 2 marks · Draw. A force of 6 N acts to the right on an object. Draw an arrow to represent this force. Use a scale of 1 cm = 2 N.
▸ Question 4 · 2 marks · Explain. Explain the difference between speed and velocity.
▸ Question 5 · 3 marks · Describe. A book rests on a table. Describe the forces acting on the book. State the type of each force.
Question 1 · 2 marks · State
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“Give one example of a scalar quantity and one example of a vector quantity.” |
HOW TO ANSWER IT Command word: State. Worth 2 marks, so plan before writing.
Question 1 · mark scheme
2 marks available. Award a mark for each point made.
▸ A scalar quantity. 1 mark
▸ A vector quantity. 1 mark
▸ Model answer. Scalar: any of distance, speed, mass, time, energy. Vector: any of force, velocity, displacement, acceleration.
Question 2 · 3 marks · Complete
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“Some forces are contact forces and some are non-contact forces. Give one example of each.” |
HOW TO ANSWER IT Command word: Complete. Worth 3 marks, so plan before writing.
Question 2 · mark scheme
3 marks available. Award a mark for each point made.
▸ Contact example. 1 mark
▸ Non-contact example. 1 mark
▸ Correct link to touching or separated. 1 mark
▸ Model answer. Contact: friction, air resistance, tension or normal contact force. Non-contact: gravitational, electrostatic or magnetic force.
Question 3 · 2 marks · Draw
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“A force of 6 N acts to the right on an object. Draw an arrow to represent this force. Use a scale of 1 cm = 2 N.” |
HOW TO ANSWER IT Command word: Draw. Worth 2 marks, so plan before writing.
Question 3 · mark scheme
2 marks available. Award a mark for each point made.
▸ Length 3 cm. 1 mark
▸ Arrowhead pointing right. 1 mark
▸ Model answer. An arrow 3 cm long pointing to the right.
Question 4 · 2 marks · Explain
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“Explain the difference between speed and velocity.” |
HOW TO ANSWER IT Command word: Explain. Worth 2 marks, so plan before writing.
Question 4 · mark scheme
2 marks available. Award a mark for each point made.
▸ Speed has no direction. 1 mark
▸ Velocity has direction. 1 mark
▸ Model answer. Speed is a scalar: it has magnitude only. Velocity is a vector: it has both magnitude and direction.
Question 5 · 3 marks · Describe
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“A book rests on a table. Describe the forces acting on the book. State the type of each force.” |
HOW TO ANSWER IT Command word: Describe. Worth 3 marks, so plan before writing.
Question 5 · mark scheme
3 marks available. Award a mark for each point made.
▸ Weight downwards, non-contact gravitational. 1 mark
▸ Normal contact force upwards, contact. 1 mark
▸ Equal in size or balanced. 1 mark
▸ Model answer. The weight of the book acts downwards (a non-contact gravitational force). The normal contact force from the table acts upwards (a contact force). The two forces are equal in size.