FrictionPrepared by:

Lovelyn M. MataacTeacher

Friction

• Force that opposes the motion of an object when the object is in contact with another object or surface.

• Force that slows down or stops motion.

How FRICTION affects motion? if you roll a ball along the floor or ground, it

will slow down and stop even though no apparent force is being applied to it. The ball slows down and stops because of friction.

Friction slows down a moving object. Friction occurs when two objects rub against each other.

A car that runs on a very rough road A car that runs on a very rough road slows down due to friction. However, on slows down due to friction. However, on a smooth road, it travels fast.a smooth road, it travels fast.

A smooth surface has a very few bumps A smooth surface has a very few bumps and hollows. There is less friction on a and hollows. There is less friction on a smooth surface. A running object can smooth surface. A running object can glide or move continuously with very glide or move continuously with very little force. little force.

Smooth surface produces less friction and allows shoes and tires to slip.

On a rough surface, there are more bumps and hollows. When you push the cart on a rough road, it will travel slowly. There’s more friction acting on the moving cart. The rougher the surface, the more friction there is, thus, the slower an object moves.

Friction is lesser on a smooth, Friction is lesser on a smooth, shiny surface.shiny surface.

Friction is greater on a rough Friction is greater on a rough surface. surface.

Advantages and Disadvantages Advantages and Disadvantages of Frictionof Friction

AdvantagesAdvantages Friction enables belts to cling Friction enables belts to cling to pulleys and nails to hold to pulleys and nails to hold objects togetherobjects together..

A running car or bicycle uses friction A running car or bicycle uses friction to stop. As the driver steps on the to stop. As the driver steps on the brakes, the vehicle slows down to a brakes, the vehicle slows down to a full stop. This is possible because of full stop. This is possible because of the friction between the brakes and the friction between the brakes and the wheels.the wheels.

Walking, running, playing, writing, sitting, Walking, running, playing, writing, sitting, standing, or eating cannot be possible standing, or eating cannot be possible without friction.without friction.

Disadvantages of Friction Shoes, slippers, tires and anything that are

used for moving become worn out. Friction produces heat that causes objects to wear out.

Friction makes work tedious. Because of Friction makes work tedious. Because of the resistance, workers need to exert more the resistance, workers need to exert more effort and energy to accomplish their work effort and energy to accomplish their work to overcome resistance.to overcome resistance.

Some machines perform less efficiently and wear out faster with friction.

Friction also causes sparks, overheating, and machine breakdown.

Friction reduces speed. Even airplanes cannot fly as fast as they are able because of air friction.

Racing cars and other vehicles consume more energy to run fast and overcome the resistance of the roads.

Friction can also make speeding objects Friction can also make speeding objects to tumble down and cause accidents. to tumble down and cause accidents.

Ways of reducing friction

Smoothing out Surface ex. Applying floor wax and

scrubbing the floor.

Placing a slippery substances between two solid surfaces

ex. Grease, oil and other lubricating liquids

Using rotating objectsUsing rotating objects ex. Roller bearings, ball bearings andex. Roller bearings, ball bearings and wheelswheels

Streamlining vehicles to reduce Streamlining vehicles to reduce friction caused by air.friction caused by air.

ex. Streamlined front of ex. Streamlined front of planesplanes

Ways to increase frictionWays to increase friction New materials with more bumps New materials with more bumps

and hollows are produce for making and hollows are produce for making car brakes lining. car brakes lining.

New styles for the soles of athletes’ New styles for the soles of athletes’ shoes. Its aim is for runners to run with shoes. Its aim is for runners to run with greater speed.greater speed.

Write the letter of the best answer.

1. It is the force that slows down or stops motion.

a. Acceleration b. motion b. friction

2. Friction is always beneficial.a. True b. false

3. Friction can be reduced.a. True b. false

• 4. What is the effect of spikes on the shoes of a runner?

• A. Increase his speed• B. Increase friction• C. all

• 5. How will you decrease friction?• A. Apply lubricant• B. Polish surface• C. all

Assignment:• Bring the following tomorrow (by

group)• 1. cup• 2. plastic ruler• 3. nail (1, long)