Students should discuss this model in an attempt to build an understanding of what the microscopic surfaces may look like and how they interact with each other. Highly magnified images of filter paper, toilet paper and rubber may be a useful discussion aid and can be seen at the following site:. Students should be encouraged to explain why, in terms of the model of surface bumps pushing against each other, applying oil or lubricant to the contact surfaces can reduce the friction and allow them to move more freely.
Students should be encouraged to identify in which direction the friction force acts in a variety of simple situations and consider examples of everyday situations where friction is deliberately increased and reduced.
A good discussion example is the purpose of using hand grips and engine oil lubricants. Students should be introduced to a variety of familiar situations involving friction where there is a focus on exploiting a frictional variation which may not be immediately apparent to students.
They could explore the reasons for the wide variation in the design of shoes and in particular the soles of shoes created for specific purposes for example: running, rock climbing, ice climbing, dancing, skating and bushwalking. Encourage students to examine the frictional advantages of each of the designs. POE Predict-Observe-Explain : ask students to predict what will happen in the following situations and then get them to observe each event before attempting to explain their observations:.
After exploratory discussion, invite students to write about what a world would look like without friction. How would it be different to our existing world? What tasks could still be done and what tasks would need to be done differently? Teaching procedure -Two Minute Bursts. It is only because of friction that we are able to stop our vehicle. All of us write using either a pen or a pencil in our daily life. What happens when you hold your pen or pencil?
Have you ever tried giving a thought about it? In case you are wondering, the answer to your question lies in the phenomenon of friction. It is the friction which enables us to write. The frictional force is created when the tip of a pen or pencil is brought in contact with the surface of the paper. In the case of writing with a ball-point pen, some sort of adhesive forces is acting between the ball and ink.
When you start writing with a ball-point pen on paper, the ball starts rolling and the ink is deposited on the surface of the paper. The rolling of the ball invites rolling friction to come into play. Whereas, while writing with a pencil, sliding friction comes into action; and deposits lead on paper. A similar concept is applicable when using an eraser. You apply some force on the eraser which helps in wiping off the desired content. You might have noticed that your hands feel warm when you rub them together for a few seconds?
Friction is responsible for generating warmth in your hands. When two hands come in contact and are rubbed against each other, there is some amount of resistance which comes into play. However, if you just put your hands together, there will be no resistance, hence, no amount of friction. The action of scraping the surface of your skin back and forth against each other causes the molecules in your skin to move a little faster.
The temperature will increase when the molecules move faster. This is the reason so as to why your hands are warm when you rub them together.
Friction works against the motion and acts in the opposite direction. The amount of friction depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced. For example, you would have to push a book harder to get it moving on a carpet than you would on a wooden floor.
This is because there is more friction between the carpet and the book than there is between the wood and the book. One kind of friction or resistance is air resistance.
Air resistance occurs between the surface of a falling object and the air that surrounds it and it also works to slow the rate at which the object falls. Air resistance works with surface area, so the more surface area, the more air resistance. Think about when you drop two pieces of paper: one crumpled and one flat.
The crumpled one falls faster because there is less air resistance acting on the paper. Friction can be useful. For example, friction between our shoes and the floor stop us from slipping and friction between tyres and the road stop cars from skidding. Friction is sometimes unhelpful. For example, if you don't lubricate your bike regularly with oil, the friction in the chain and axles increases.
Your bike will be noisy and difficult to pedal. When there is a lot of friction between moving parts, energy is lost to the surroundings as heat.
Think of what happens when you rub your hands together quickly. The friction warms them up. When one object is sliding on another it starts to slow down due to friction. This means it loses energy. However, the energy doesn't disappear. It changes from moving energy also call kinetic energy to heat energy. By rubbing them we generate friction and, therefore, heat.
Friction is the resistance of motion when one object rubs against another. Anytime two objects rub against each other, they cause friction. Friction is also a great help to us. After all, we would all just be sliding around everywhere if there wasn't friction to keep us steady! Friction is also used in car brakes, when we walk or climb a hill, in sandpaper, making a fire, and more. Friction has many uses in life.
You light a match using friction. As you strike a match, friction creates enough heat to ignite a chemical compound in the match head that then burns the rest of the match head.
Car brakes work because of friction. Shoes designed for some sports have special soles to use friction to your advantage. Football boots have studs to increase friction by sticking to cracks in the ground. A violinist puts rosin on his bow to increase friction between the bow and the violin strings, therefore producing sound. However, friction can also be a real nuisance. If a door hinge squeaks, the noise is caused by friction.
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