Question

Give two examples each of the following case:- (3) Increasing friction by pressing the objects tightly​

Answer 1

Answer:

push friction

Explanation:

because they pressing

Answer 2

Answer:

Q: What are some ways in which friction can be increased in a situation where friction is useful?

A: there are some ways typically used in such situations:

• use right materials. While steel on steel may have low friction, some organic fibrous materials perform much better (they used to contain asbestos, but this is a strong carcinogen so a bug no-no currently)
• keep the surfaces clean. A drop of oil can reduce the friction many times. Sometimes this is what you want, so you use lubricants, sometimes this is not. Rinse the surfaces with some organic solvent or let the oil burn out.
• keep the surfaces cool. Hot surfaces typically have less friction - good example is how the car brakes will fade when hot
• use angles - e.g. the V-belt where the wedge-shaped belt is pushed in between the rims so the contact force between the belt and a rim is much bigger than the actual belt tension. Also, the contact surface is bigger thus less prone to overheating.
• use toothed belts or gears instead of smooth ones
• use sand - train locomotives carry on the dry sand in the containers and have a system (automated or manual) that delivers this sand right before the wheels. This helps reduce the slip during a kickstart or sharp braking.
• use dedicated substances. My grandpa applied some rosin on the leather belt in his machines. It became a little sticky, but there slip was significantly reduced
• provide sufficient contact (normal) force. So use hydraulic brakes that amplify the contact force. Maintain a proper tension of a belt (e.g. with spring-loaded rollers)
• in belts, also make sure the belt embraces enough of the wheel circumference (this is the wrap angle). If too small, increase it with dedicated belt guiding rollers.