Science PPT

Name:-Nihar.sanjeev.satpute

Topic:-Friction[Physics]

Place:- 590004 khasbag belgaum, karnataka

India

standard:-10th

Friction[introduction] Friction is a force that opposes the relative motion

between two surfaces of objects in contact. The force of friction always acts in a direction opposite to that of the applied force. Friction exists between two surfaces due to irregularities on the surfaces of the objects in contact, interlocking of micro-level irregularities of the two surfaces and ploughing of harder surfaces into smoother surfaces. 

For exampleSuppose you decide to ride a skateboard.You push off the ground and start moving.According to Newton’s First Law of Motion, if no other

forces are acting on your skateboard, you will continue to move….BUT

What happens?Your skateboard slows down because of friction.Friction is the force that opposes motion between two

surfaces that are touching each other. The amount of friction depends on two things:

Kind of surface.Forces pressing the surfaces together.

Your skateboard slows down because of friction.Friction is the force that opposes motion between two

surfaces that are touching each other. The amount of friction depends on two things:

Kind of surface.Forces pressing the surfaces together.

What causes frictionEven though a surface may look smooth, if you magnify

the surface it isn’t smooth. Everything is made of molecules. The molecules come

together to make bumps. Some surfaces have molecules that leave large bumps and some leave smaller bumps, but all surfaces have bumps.

Microwelds occur when two bumpy surfaces are rubbed up against each other they stick together.

Factors That Affect Friction

• Roughness of the surface• the extent to which the two surfaces

press together• Nature of the surface

Types of Friction There are three types of friction that exist between solid surfaces. They

are static friction, sliding friction and rolling friction. Frictional force that comes into action before the start of the motion of an object is called static friction.  Example: a box placed on the floor. When an object slides over another surface, the frictional force that comes into action is sliding friction. Example:  a boy sliding on a slide. The frictional force exerted when an object rolls over a surface is called rolling friction. Example:  rolling ball on the ground. It is found that: 

Rolling friction < sliding friction < static friction.

The frictional force exerted by fluids when objects move through them is called fluid friction or drag.  

There are four types of friction

static friction sliding friction

rolling friction Fluid friction

Four types of friction and their definition

Static friction:-when a force is applied to an object but it does not cause it to moveexample: pushing on a wall

Fluid friction:-occurs when a object moves through a fluid, meaning either a liquid or gasexamples: skydiving, swimming

Sliding friction:-occurs when solid surfaces slide over each otherexample:-falling on the pavement

Rolling friction:-occurs when solid surfaces slide over each otherexample:-falling on the pavement

Effects of Friction Friction produces heat.  Friction causes wear and tear. Friction opposes motion

Advantages of FrictionFriction between pen and paper enables us

to write on the paper. Friction between our feet and the ground

allows our movements like standing, walking and running

Friction between the surface of the road and tyres of our vehicles allow the vehicles to move without slipping

Disadvantages of Friction

Friction causes moving objects to stop or slow down.

Friction produces heat causing wastage of energy in machines

Friction causes wear and tear of moving parts of macinery, soles of shoes, etc

Methods of Increasing and Reducing Friction

In real life, there are circumstances where we have to increase the friction and minimize the friction. Friction can be increased by increasing the roughness of the surfaces in contact. For example, treading of shoes and tyres is done to increase friction. When friction is undesirable we have to reduce the friction. Friction can be minimized by using lubricants like oil and grease and by using ball bearing between machine parts. A substance that is introduced between two surfaces in contact, to reduce friction, is called a lubricant. Fluid friction can be minimized by giving suitable shapes to the objects moving in the fluids.

Friction Is A Necessary Evil

There are instances in daily life where friction is a necessity. For example, without friction, we cannot hold objects in our hands; we cannot walk and cannot light a match stick. Sometimes friction is not desirable, for example  friction between machinery parts, which causes wear and tear. As friction is advantageous to us it is considered as a friend but due to its disadvantages it is a foe. Depending on the circumstance, friction can be a help or a hindrance. Thus it is a necessary evil. 

Thank-you