Friction 🔥

Friction & Its causes

Friction: The force which opposes relative motion b/w 2 surfaces in contact

• Applied force = P

• Frictional force = f

Relative motion : motion of an object with respect to the other object, aka both objects r moving

Causes :

• Interlocking between irregularities: irregular parts of a surface get interlocked

  

• Bond Formation : When 2 surfaces r close to each other, the attractive forces between the molecules of the surfaces cause a bond to form, which increases the resistance to motion.

  • lekin, these bonds r temporary

Factors affecting Friction

1. Nature of surface - rough surface = more friction , smooth surface = less friction

2. Normal Force/ Pressing force - matlab, with how much pressure each surface is pressing the other

   • If the weight of one thing is more, pressing force will be more

   • more pressing force = more friction

   • Less pressing force = less friction

Types of Friction ⚡

1. Static Friction - When u apply force on a body, but it still doesn’t move, friction is stopping it from moving

   • Until the body is in rest, static friction is acting upon it

   • So, the force u apply on the body is being cancelled by the frictional force

   • Max amount of friction

   • The force friction is applying is variable, it can change from 0 to max value (limiting friction)

   • Limiting friction - the maximum value of static friction just befor the object begins to move

   • The moment body starts to move, friction ka value will decrease

2. Sliding Friction - Whenever a body is sliding on another surface

   • When a body is moving in relation to another surface

   • Value of sliding friction is the same, can’t differ

   • Also called Kinetic friction & Dynamic friction

3. Rolling Friction - When an object rolls over a surface

   • Least amount of friction

Why sliding friction is less than static friction?

• Static friction is the maximum frictional force acting on an object and it decreases in sliding friction, so once static friction is overcomed, lesser force is require to move to object

• When a body is at rest, it gets good time for bond formation, but when a body is sliding it doesn’t get time to form bonds and stronger bonds = greater friction

Importance of Friction

• Being able to walk

• Writing

• Holding things

• Breaks in a car

• Lighting match sticks

Increasing ⇡ and Decreasing ⇣ Friction

• To increase - Increase the roughness of the surface (grooves)

• To decrease - Making surface smoother (grease)

  • Making stuff roll, by putting wheels, logs

  • Ball bearings - sliding friction is converted to rolling friction to help

Friction in machinery parts -

• Lubrication, putting oil & grease

• Ball bearing converts sliding friction to rolling friction

Fluid Friction 🌊

The friction experienced when moving through a fluid = Fluid friction

• The friction applied by liquids and gases

• Fluid Friction = Drag force

Factors affecting

1. Relative speed of the body with respect to the medium ,i.e, how fast a body in the fluid is moving

2. Nature of the medium - Higher viscosity / density = higher friction , Lesser viscosity / density = less friction

3. Shape of the object - More surface exposed = more friction , Less surface exposed = less friction

   • Streamlined shape reduces the friction