Friction forces and benefit physics year 8.pptx

physic year 8

1. Connect How are these images linked?

2. Must : We are learning what friction is and how it affects the movement of objects. Could : 1) Describe the effect of friction on moving objects. 2) Describe how to reduce friction 3) Understand when friction can be useful and have disadvantage. Learning Outcomes

3. If you rub your hands together they get warm. There is resistance to the rubbing motion. What is the name of this resistive force called? What causes this force? Your hands might look smooth, but on a microscopic level they have rough surfaces. So when you rub your hands together you feel the resistive force of friction. What is friction? It is called friction . Share new Information Friction is a force that resists movement because of contact between surface

4. We need to push the things to get them to move. If you push the books on the table, but the book does not move. Why this happen?? The forces are balanced. To move the book: Uneven surface of the table will produce friction force. If your force is bigger than friction force, it will create unbalanced force. The book will move

5. Friction always tries to slow moving objects down. Reducing friction People often want to reduce the friction, to get more faster or reduce the damage. Slippery slide can accelerate the child Lubricant on the chain of the bicycle can have smooth surfaces and less of friction Ball-bearings in the wheels of skateboard. It will roll over each other, create less friction How to reduce the friction????

6. Can help things to move For walk, friction acts between your feet and the ground For vehicle to move, the friction between tyres of the car and the road To stop the object The force between the brake and the wheels will stop the bicycle, cars Friction can be useful What will happen if there is less of friction on the slippery road?

7. Effects of frictional forces Share new Information

8. CAUTION Fun Science experiment Ahead!!

9. Practicals  Rub your hands together very fast! Explain what happens to the person next to you. Write a short sentence or two to say what you did and what happened. My hands became _ _ _ when I .........because of F_ _ _ _ _ _ _. F_ _ _ _ _ _ _ produces heat  Activity

10. 2. a) Put a 500g mass in your shoe and put it on a ramp with a force meter (Newton meter) attached to the back. b) Write down how much force you need to stop your shoe sliding down the ramp. c) Do the same thing with a different surface. What do you notice?  Activity

11. Force needed to stop the shoe sliding on a ______________ surface = _____ N Force needed to stop the shoe sliding on a ______________ surface = _____N Conclusion: The _________ surface needed __ N to stop the shoe sliding. The ____________ Surface needed __ N. This means that the first/second surface had a greater/lower friction. Activity

12. Plenary Discuss with your partner where you think the force arrows should go on your diagram. Explain your reasons. Will the force arrows be balanced? Keywords: Weight, Reaction, Friction, Pull Activity

13. Pull Friction Reaction Weight Activity

14. Friction is good… Without friction we wouldn’t be able to walk, sit in a chair or drive safely. Everything would keep sliding and falling over. We need friction between our feet and the ground or we would not be able to stand up. When you are riding a bike and press the brakes, friction slows your bike down.