FRICTION By Leena gawas Sonam gosavi Neekita Bhowar

FRICTION By : - Leena gawas Sonam gosavi Neekita Bhowar

FRICTION • Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

Types of friction • Dry friction: - is a force that opposes the relative lateral motion of two solid surfaces in contact. It is subdivided into 1) static friction ("stiction"): - between nonmoving surfaces. It exists between a stationary object and the surface on which it's resting.

2) kinetic friction: - between moving surfaces. Also called as sliding friction. Eg. Rubbing both hands together to create heat

• Fluid friction : - describes the friction between layers of a viscous fluid. Also called as viscosity. • Rolling friction: - is a force that slows down the motion of a rolling object. Ball or wheel has rolling friction when rolled on a surface.

Factors affecting friction ØTypes of surfaces ØHow hard the surfaces are pushed together ØMass of object F=µN (N=mg)

What increases Friction • Friction increases when the force between two objects is increased.

What increases friction • Rough surfaces A pair of rough surfaces will have more friction than a pair of smooth surfaces, because the “peaks” of one surface can fall into the “valleys” of the other. • Weight of an object Force friction= weight x coefficient of friction So as the weight increases so does the amount of friction.

Friction increases when surface area of an objects increases

What decreases Friction • To reduce the amount of friction, apply a lubricant between two surfaces. • Motor oil, wax, and grease are examples. • Friction can also be reduced by rolling, rather than pushing, an object.

Measuring Friction Measuring friction have been investigated for more than 2500 years. Amonton's law was originally published by Da Vinci and later rediscovered by Amonton's law states that the friction depends only on the force normal to the contact plane. From this, the friction coefficient can be defined as: μ= F / N where F is the force required to move an object on a horizontal surface and N is the load normal to the surface.

Friction Measuring Equipment • T 2 GO Portable Continuous Friction Measuring Equipment, CFME • T 2 GO, which can measure friction on any surface both dry and contaminated. It is ideal for measuring in areas where it might be difficult to get access to with a larger trailer or vehicle type friction tester.

• An essential tool in the operation of traffic infrastructure during winter conditions. • This serves as a guidance to initiate remedying actions such as snow removal, distribution of de-icing chemicals and speed reduction, in order to enable a safe use of the traffic infrastructure.

Friction in plants • The stability of twining vines under gravitational loads suggests an important role for friction. • The coefficient of friction, μ, between vine stems and wood is high, often five times greater than between leather and wood.

An interesting difference in frictional properties was the upright hairy segments had larger frictional interactions than the inverted hairy segments.

FRICTION IN ANIMALS • Many animals have the natural ability to move on vertical walls and ceilings. • They attach to surfaces using claws, soft and hairy pads. • Recent studies have indicated that the frictional forces generated by these structures not only control the movement of animals but also significantly increase the reliability of their attachment.

• Snakes use Sliding Friction as they slither along. • They use branches and sticks to push and slide along the ground or in trees. • In fact their scales are perfectly designed to keep the snakes from sliding backwards or sideways while climbing

• Snails use fluid friction as they give out slime layer to protect their body from rough surface and improve movement. • It also acts as shield against parasites.

• Flies, geckos and beetles have ability to move on inclined surface using hairy pads. • Soles of feet have elastic epidermis covered with setae which control friction and genertes opposite frictional forces.

• Snapping turtles great size makes it impossible for predators to prey on them unlike small turtles. • Static friction makes it harder for turtle to be moved by predator.

• The body of the mother-of-pearl moth caterpillar escapes predators by anchoring its tail, recoiling, and uses rolling friction for escape. • By turning into a wheel, the caterpillar moves some 40 times faster than its normal walking pace.

Uses of friction • When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy (that is, it converts work to heat). • This property can have dramatic consequences, as illustrated by the use of friction created by rubbing pieces of wood or stones together to start a fire

• In space, meteors and comets have no force to slow them down. • As they hit the Earth's atmosphere, however, not only does the atmosphere's friction slow them down, it tends to break them apart into smaller pieces, thereby lessening their impact on the Earth's surface.

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