Exploring Forces · Learner pages

Lesson 1 · Recognise what a force can change

Identify interacting objects and describe changes of speed, direction or shape.

Name or initials: ____________   Date: ____________

A force is a push or pull arising from an interaction. We identify its effect on a chosen object and do not infer absence of force from stillness alone.

1. Name the interacting objects. When a hand pushes a book, the hand and book interact. State which object receives the force; a force is not a substance stored inside the book.
2. Look for a change in speed. A gentle push can start a stationary toy moving. A contact force opposing a moving toy can slow it. Record the change, rather than assuming every push must speed it up.
3. Look for a change in direction. A moving soft ball redirected sideways changes direction. A force can change direction even when a speed reading alone seems unchanged.
4. Look for a change in shape. Pressing a sponge changes its shape. A visible change is evidence of an interaction, but an object staying still does not prove that no forces act on it.

Worked example: A soft toy ball moves east before touching a guide and north afterward. Its direction changed. That observation supports a force interaction between ball and guide; it does not give the numerical size of that force.

1. A sponge becomes flatter when gently pressed. The observed effect is…

   1. a change of shape · 2. a change of chemical element · 3. proof of zero force

2. A force can change…

   1. only colour · 2. speed, direction or shape · 3. only the name of an object

3. A book rests on a table. Which statement is correct?

   1. No force acts because it is still · 2. Only the table exists as an interacting object · 3. Earth pulls down and the table pushes up

Discuss: Choose a safe everyday example such as opening a drawer or gently pressing a sponge. Name the two interacting objects, the object studied and the change observed.

Lesson 2 · Use friction evidence fairly

Identify friction on a sliding object and plan a controlled comparison.

Name or initials: ____________   Date: ____________

Contact forces require touching objects. Friction resists relative sliding or attempted sliding between contacting surfaces. The simplified model here uses a block sliding on a stationary surface.

1. Identify contact. A hand pushing a box and a string pulling a toy involve contact. The contact can be transmitted through another object such as a rope.
2. Track sliding and friction separately. For a block sliding right across a stationary table, friction on the block acts left. Friction opposes relative sliding between touching surfaces.
3. Compare surfaces with controls. To investigate surface effects, keep the object, initial motion and method as similar as possible. Change the surface and repeat the observations; one unequal hand-push is not a fair force measurement.
4. Use evidence with limits. Illustrative trials show shorter stopping distances on cloth than on the smooth board. With comparable starting motion, this supports greater resistance for this tested pair. It does not establish the same ranking for every material pair.

Worked example: Illustrative stopping distances for the same block are board: 40, 42, 44 cm; cloth: 18, 20, 22 cm. Means are 42 cm and 20 cm. If starting motion and other conditions are comparable, the cloth gives greater resistance in this test. Without comparable starts, the conclusion is weaker.

1. A block slides right across a stationary table. Friction on the block acts…

   1. right because it follows motion · 2. up because all forces point up · 3. left, opposing the sliding

2. Which comparison is fairer for testing surface effects?

   1. Same block and comparable starts on each surface · 2. Different blocks, different pushes and different slopes · 3. Only one favourite trial with no record

3. Why repeat stopping-distance measurements?

   1. To force every answer to match · 2. To see variation and improve the evidence · 3. To make units unnecessary

Discuss: Plan the records needed to compare two safe flat surfaces using a lightweight toy. State how you would keep starting conditions similar and repeat trials. A plan and supplied data are sufficient; do not use roads or high-speed objects.

Lesson 3 · Distinguish forces that act across a gap

Use examples to separate magnetic, gravitational and electrostatic interactions.

Name or initials: ____________   Date: ____________

A force does not always require touching. Classify the interaction from the objects and evidence, not just from the presence of movement.

1. Recognise magnetic interaction. Two suitable magnets can attract or repel without touching. Unlike poles attract and like poles repel; the gap shows that contact is not required.
2. Distinguish force from material claims. A magnet attracts some materials such as iron, not every metal or every object. Test evidence is needed before classifying an unfamiliar material.
3. Recognise Earth’s gravitational pull. Earth pulls nearby objects towards itself without requiring contact. Weight is this gravitational force and is measured in newtons; mass is measured in kilograms.
4. Recognise electrostatic interaction. A charged comb can attract small paper pieces without direct contact. This is electrostatic interaction, not evidence that the comb became a magnet. The drawing shows a model, not invisible field lines measured in an experiment.

Worked example: A metal sample moves toward a magnet before touching it. This supports magnetic attraction for that sample. It does not show that all metals are attracted. In a different demonstration, a charged comb attracts paper: that supports electrostatic interaction instead.

1. Which interaction can occur without contact?

   1. A hand pressing a sponge · 2. A magnet attracting iron across a small gap · 3. A rope pulling a box through touch

2. Two like magnetic poles facing each other tend to…

   1. repel · 2. always attract · 3. lose all interaction

3. Which pairing correctly distinguishes mass and weight?

   1. Mass in N; weight in kg · 2. Both are always measured only in centimetres · 3. Mass in kg; weight in N

Discuss: Sort these situations and justify each: a hand pressing clay, Earth pulling a falling leaf, two magnets attracting across a gap, and a charged comb attracting paper. Use the descriptions; no electrical source is needed.

Final check · Set 1

Try one set after the lessons. Use the other set after reviewing any errors.

1. A soft ball changes direction after touching a guide. Evidence supports…

   a force interaction with the guide / no force because the ball is soft / a change in the ball’s mass must have occurred

2. Which is the symbol for the SI unit of force?

   kg / N / cm

3. A block slides left on a stationary table. Friction on the block acts…

   left / only upward / right

4. Changing block mass and surface together makes a comparison…

   harder to interpret because two factors changed / automatically more accurate / proof that surface has no effect

5. A charged comb attracts paper across a gap. The interaction is…

   magnetic by definition / electrostatic / only muscular contact

6. Which conclusion follows from one iron clip being attracted to a magnet?

   Every object is magnetic / Every metal is magnetic / This clip shows magnetic attraction in the test

Final check · Set 2

Try one set after the lessons. Use the other set after reviewing any errors.

1. An unmoving book on a table…

   has no interacting objects / can experience balanced forces / has no weight

2. Pressing soft clay mainly demonstrates a possible force effect on…

   shape / the unit of time / its chemical identity

3. Which trial record is most useful?

   Only “it went far” / Only the colour of the toy / Surface, starting method, repeated distances and units

4. Friction on a sliding block is classified as…

   a contact force / always magnetic / always absent on smooth surfaces

5. Unlike magnetic poles facing each other tend to…

   repel / attract / become gravitational only

6. Weight describes…

   how many centimetres long an object is / the same quantity as volume / the gravitational force on an object