Friction in nature and technology
Answers are for parents and teachers.
1
Name one situation at home where friction is useful and one where it is harmful.
Useful: shoe soles; harmful: squeaking and wear of door hinges (oiling helps).
2
Which parts of a bicycle need more friction and which less?
More: tyres, brake pads, pedals; less: chain, bearings, axle.
3
Why is hard braking dangerous on a slippery road?
The wheel can skid and cause a fall.
4
Why is a car engine lubricated?
To reduce friction and wear between parts.
5
A 1000 kg car skids while braking on dry asphalt (μ = 0.5, g = 10). Sliding friction force (N)?
5000