III, Name the following:
1. Type of friction involved when an object just starts moving:___
2.Type of friction involved in keeping an object moving:______
3. This produces heat on rubbing the palms together:______
4. This is used between moving parts where it is not advisable to use oil:______
5. Three lubricants:____, ____, ___
6. Type of friction that is smaller than sliding friction:
____
Answers
1)=Sliding friction is friction that acts on objects when they are sliding over a surface. Sliding friction is weaker than static friction. That's why it's easier to slide a piece of furniture over the floor after you start it moving than it is to get it moving in the first place. Sliding friction can be useful....
2)=Static friction operates between two surfaces that aren't moving relative to each other, while kinetic friction acts between objects in motion..
3)=friction
If you rub your hands together for several seconds, you'll notice that your hands feel warm. That warmth is caused by a force called friction. When objects like your hands come in contact and move against each other, they produce friction....
4)=Movement becomes smooth. The substances which reduce friction are called lubricants. In some machines, it may not be advisable to use oil as lubricant. An air cushion between the moving parts is used to reduce friction...
5)=There are three different types of lubrication: boundary, mixed and full film. Each type is different, but they all rely on a lubricant and the additives within the oils to protect against wear. Full-film lubrication can be broken down into two forms: hydrodynamic and elastohydrodynamic....
6)=The force of friction depends on the area of contact between the two surfaces. As the area of contact is less in the case of rolling than in the case of sliding, rolling friction is less than the sliding friction. Rolling friction is the resistance to motion experienced by a body when it rolls upon another...