Friction Flashcards
Friction is a force that opposes the motion of an object.
Explain what this statement means?
“Friction is a force that opposes the motion of an object’.”
- A force is a push or pull.
- Motion means something is moving.
- Opposes means goes against.
So, friction is a type of force that tries to stop things from moving.
Give two examples from everyday life in which friction occurs.
- When a car is moving, it has to push through the air in front of it. The air pushes it back – this is called air friction. It slows the car down.
- When you walk or run, your shoes rub against the ground. This rubbing creates friction which stops us from slipping.
What is Friction?
Friction is a force which occurs whenever a moving object rubs against another object.
Friction always opposes the motion of an object.
Whenever the force of friction is present, useful energy will normally be wasted.
What type of energy does friction always produced?
Heat (thermal energy)
Whenever the force of friction is present, useful energy will normally be wasted.
Where does this wasted energy normally go?
The heat usually spreads out into the surroundings, like the air, the object itself, or nearby surfaces.
That’s why we call it wasted energy – it’s not being used to do something useful.
Whenever the force of friction is present, useful energy will normally be wasted.
Give an example of when the energy produced is not wasted by actually useful.
A good example is rubbing your hands together to warm them up.
Friction between your hands produces heat, and in this case, that heat is useful—it keeps your hands warm!
There are several factors that affect the size of the force of friction acting on an object.
Team Aloysius are developing a new ‘super car’ to race in the next schools Grand Prix and have narrowed their design choice down to two final options drawn below. Mr O’Duffin of the Physics Department has opted for Design A (a sleek car similar to a lambourgini) whilst Dr Swan from the Biology Department has gone
for Design B (an old fashioned box shaped car) .
By considering frictional force,
a) State who has made the better choice
b) Give at least two reasons to support your answer.
a. Mr O’Duffin with Design A
b. Design A is more streamlined, which means it has less air resistance (air friction). This helps the car move faster and more smoothly through the air.
Design B (box-shaped) creates more air friction, because its flat front pushes against more air, slowing the car down more than Design A.
What factors affect the size of the force of friction.
Investigate through experiment ways of reducing the force of friction to allow things to move faster and increasing friction to slow things down - PUCK & BALLOON
Investigate through experiment ways of reducing the force of friction to allow things to move faster and increasing friction to slow things down - RUSTY HINGE
Investigate through experiment ways of reducing the force of friction to allow things to move faster and increasing friction to slow things down - WOODEN BLOCK
Engineers and scientists work with sportsmen and women to design
equipment and clothing which will allow them to perform better.
a) Give two examples of when the sports men and women would want to INCREASE the forces
of friction as much as possible.
b) Describe how they might do this in each case.
Runners:
* WHEN: to stop them slipping when they push off the ground.
* HOW: Runners wear shoes with spikes or grippy soles. The spikes dig into the track, increasing friction and helping them get a strong push without slipping.
Gymnastics
* WHEN: to help them grip the bars better and avoid falling.
* HOW: Gymnastics use chalk on their hands to keep them dry and improve grip (more friction between hands and bars).
Engineers and scientists work with sportsmen and women to design
equipment and clothing which will allow them to perform better.
a) Give two examples of when the sports men and women would want to REDUCE the force of friction
b) Describe how they might do this in each case.
Swimmers:
* WHEN: so they can move through the water more quickly and smoothly.
* HOW: Swimmers wear tight, smooth swimsuits (often made from special materials) and swim caps to make their bodies more streamlined, so there’s less friction with the water.
Cyclists:
* WHEN: to reduce air resistance and go faster.
* HOW: Cyclists wear tight-fitting clothing and ride aerodynamically-shaped bikes. Their position on the bike is also low and sleek to reduce air friction (air resistance) as they ride.
What are forces changing:
A person landing on a trampoline
Shape – the trampoline stretches and changes shape.
Speed – the person slows down as they land.
Direction – the person might bounce back up!
What are forces changing:
Wind blowing a model aeroplane off course
Direction – the wind changes the direction of the aeroplane.
Speed – the wind can also make it speed up or slow down.
What are forces changing:
Applying your bike’s brakes when cycling down a hill
Speed – the brakes reduce the speed.
What are forces changing:
An apple falling from a tree
Speed – it speeds up as it falls due to gravity.
Direction – if it bounces or the wind blows it slightly, the direction might also change.
What are forces changing:
A tennis ball as it hits the strings of a racket
Shape – the ball squashes on impact (even if we don’t see it easily).
Speed – the ball can speed up or slow down.
Direction – the racket changes where the ball goes.
What are forces changing:
Rolling out pastry to make a pie.
Shape – the pastry is flattened and stretched.
What are forces changing:
The Moon in orbit around the Earth (think carefully about this one!)
Direction – the Moon’s speed stays roughly the same, but gravity constantly changes its direction, keeping it in a curved path (orbit).
