Year 7 Science · Unit 3 · Lesson 3
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Each word is used at most once. Two words are not needed: cross them out.
is a contact force that opposes motion between two surfaces. A book sitting still on a tilted desk is held in place by friction. Once the book slides across the desk, friction acts, which is also called kinetic friction. A bike wheel on the road feels friction, which is much smaller than sliding friction. A swimmer moving through water feels friction, also called drag. Friction in a car’s brakes is , because it slows the car safely. Friction between moving metal parts in an engine is , because it wears them down and wastes energy.
1. A box is pushed east across the floor. Which way does friction act on the box? Explain why, using the high points of the two surfaces.
Odd one out
Each row starts with what to compare. Three items in the row are alike and one is not. Circle the odd one out and write why on the line.
a. Type of friction: a brick resting on a sloping drive · a phone resting on a tilted book · a runner’s shoe just before she pushes off · a sled sliding down a sand dune
b. Useful or harmful: brakes slowing a car · a pencil leaving graphite on paper · a rope held by a climbing anchor · metal engine parts wearing down
c. Increases or reduces friction: oil on a bike chain · streamlining a car · ball bearings in a wheel · grip tape on a skateboard deck
d. Changes the friction between two solid surfaces: how rough they are · how hard they are pressed together · oil between them · their colour
2. Moving a heavy cupboard across a floor is much easier on small wheels (castors) than dragging it. Use the terms rolling friction and sliding friction to explain why.
Read the data: how far does the block slide?
Scenario
A class gave the same wooden block the same push along four different surfaces. They measured how far it slid before it stopped.
| Surface | Polished wood | Vinyl | Carpet | Rubber mat |
|---|---|---|---|---|
| Distance slid (cm) | 180 | 120 | 30 | 10 |
Source: sample class results.
3. Draw a column graph of Table 1. Label both axes and give the graph a title.
4. Which surface had the most friction with the block? Use Table 1 to explain how you know.
5. Name two things the class had to keep the same to make this a fair test.
6. A cyclist says: “Friction is bad. My bike would be better with no friction at all.” Use examples from a bicycle to explain why she is wrong. Name the type of friction in each example.
Fill the gap
friction; static; sliding; rolling; fluid; useful; harmful. Not used: gravity, tension.
Question 1
West, the opposite way to the motion (1). The high points of the box and floor interlock and resist being dragged past each other (1). [2 marks]
Odd one out
1 mark per row. a: the sled, sliding friction; the brick, phone and shoe are held still by static friction. b: engine parts wearing down, harmful; the others are useful. c: grip tape increases friction; the others reduce it. d: colour has no effect; roughness, pressing force and oil all change friction. [4 marks]
Question 2
Dragging means sliding friction: the base scrapes along and its high points must shear past the floor’s (1). Castors swap this for rolling friction, which is much smaller because the wheel touches at a small patch that is set down and lifted up, not scraped (1). [2 marks]
Read the data: how far does the block slide?
3. Axes labelled (surface; distance slid in cm) with an even scale (1); four columns at the correct heights (1); a title (1). [3 marks]
4. The rubber mat (1): with the same push the block slid only 10 cm there, the shortest distance, so friction stopped it fastest (1). [2 marks]
5. Any two, 1 each: the same block (same mass); the same size of push; pushed in the same way from the same start line; distance measured the same way. [2 marks]
Question 6
Marking guide: 1 she is wrong; 1 useful example with type, e.g. brake pads rubbing on the wheel (sliding friction); 1 second useful example with type, e.g. static friction stops her shoes slipping on the pedals (accept tyres gripping the road as static, not rolling, friction); 1 harmful example with type, e.g. the chain rubbing (sliding friction) wears it and wastes energy, or air resistance (fluid friction) slows her; 1 how it is reduced: oil the chain, ball bearings, or crouch to streamline. [5 marks]
Model answer: She is wrong. Her brakes slow her by sliding friction between pads and wheel, and static friction keeps her shoes on the pedals. Some friction is harmful: sliding friction in the chain wears it and wastes energy, so she oils it.
Common error: calling the friction on a still object sliding friction.