Is There Friction With Constant Velocity: Why, When, How And Facts

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This article answers the question “is there friction with constant velocity?” It should be noted that in constant velocity motion also, friction comes into play.

Friction is the result of two objects rubbing against each other. The irregularities on the surface are the sole reason that gives rise to friction. No real surface is ideally smooth and will always have some amount of irregularities in them. Let us see more about the role of friction in constant velocity motion.

What is velocity?

It the rate at which the displacement changes with time. Mathematically velocity can be given by dx/dt. The terms x and t hold their conventional meanings that is displacement and time respectively.

Velocity of an object can be variable, it can be constant or it can even be zero. Any object cannot move itself, it needs an external force to drive the object from one place to another. If the applied force is constant then the velocity will be constant, if the froce is variable then the velocity will also be variable. If the frce is zero, the object will not move.

What is friction?

Friction can be defined as the resisting force to an object when it is being rubbed on a rough surface. Generally all the surfaces are rough.

For easy calculations we consider the value of friction as zero. In real life, there is no such thing as a smooth surface. There always exists some roughness even in the smoothest appearing finishes.

is there friction with constant velocity
Image: Friction between two blocks

Image credits: CaoHao, Friction between surfaces, CC BY-SA 4.0

What is co efficient of friction?

Co efficient of friction is a ratio of two forces that are frictional force and normal force. A reaction force is applied by the ground to the object which is equal to the weight of the object itself (only for flat surfaces).

Mathematically, co efficient of friction can be given as follows-

μ = F/N

where,
mu represents co efficient of friction

F represents frictional force

N represents normal or reaction force

How to minimize friction?

Although friction is desirable for doing daily tasks. But excessive friction leads to loss of useful energy. To reduce friction we can do the following-

  • A good surface finish- A good surface finish can be obtained by surface finishing processes like grinding and buffing. These leave a finer finish, although not completely smooth but they significantly reduce the amount of friction.
  • Using of lubricants– Lubricants go and settle between the rough areas on the surface. This way the object gets smoother and friction becomes lesser.
  • Making the contact surfaces round-Round surfaces have lesser friction as compared to the flat surfaces. Round surfaces create rolling friction which is very less than the conventional friction.
  • Applying powder on the surface- Sprinkling of powder is nothing but spreading fine particles on the rough surface. These fine particles settle in the rough areas of the surface giving away a surface with less friction.

What is surface finish?

If we want to define the nature of a surface, then it can be done by measuring its surface finish. It is the measure of roughness or smoothness of the surface.

Surface finish can be measured by various methods which include both contact and non contact methods. Using of profilometers and methods like confocal micrometry, focus variation and photogrammetry etc can be used for measuring the surface finish of the object.

What is kinetic friction during constant velocity?

Kinetic friction is the type of friction that comes into play when the object has started its motion (Static friction comes into play before the start of motion).

In a constant velocity motion, kinetic friction is that value of force that is exerted o the object to keep it moving at constant velocity motion. The magnitude of kinetic friction will be equal to that force which is responsible for keeping the object at constant velocity.

How do you find kinetic friction with constant velocity?

Finding the value of kinetic friction in a constant velocity motion is a very easy task. The friction acts continuously on the object while it is moving.

To keep the object in constant velocity motion, we need to continuously apply force on the object. The magnitude of this force is equal to the magnitude of kinetic friction acting on the object. In a nutshell, value of kinetic friction is equal to the force needed to keep the object moving in constant velocity.

Types of friction

Based on the motion of the object, friction are classified into types. Types of friction depend solely on the type of motion of the object. The types of friction are-

  • Static friction– Static friction as the word suggests, occurs oly when the object is at rest. The minimum force required to make the object start moving is called as the static friction.
  • Kinetic friction– This is a type of frictional force that comes into play only when the object is moving hence the term kinetic friction. Kinetic friction is the force responsible for stopping of the vehicle when the force responsible for object’s motion is lifted.

Negative effects of friction

Friction can be both useful to us and undesirable to us depending on the application where the friction is taking place. The places where friction is not desired are given below-

  • Excessive friction between gears– When there is excessive friction between two meshing surfces, the surfaces become hot and result in loss of mechanical energy. Loss of mechanical energy directly relates to burning of more fuel which directly impacts the environment.
  • Friction between machine elements– Again, the mechanical components will be working at low efficiency. This means that more fuel will burn, it will not be god economy wise also.
  • Cars driving on a bumpy road– Bumpy roads are nothing but roads having high magnitude of roughness. Cars will have to burn more fuel to push through these roads.
  • Friction burns– When there is excess friction, the heat generated by the friction can also result in burns. For example, if we fall on the ground while running, then our skin gets rubbed with the ground resulting into bruises and burns.
  • Aerodynamic drag- Aerodynamic drag is the frictional drag created by the wind. This drag is responsible for slowing down the aeroplane. If there is more drag then the aeroplane will have to burn more fuel to maintain its cruising velocity.
  • Door hinges– Door hinges are made of metal, when the metal gets rusted, the friction between the hinge elements increases, so the movement of door becomes noisy and improper. Regular oiling needs to be done.
  • Cycle parts- The chain used in cycle may get rusted and create more friction. Due to more friction, the efforts needed to push the cycle will be more which will result into unnecessary exertion.

Positive effects of friction

The friction is useful to us in many ways. Without friction, many day to day activities would have come to halt.

The positive effects of friction are given below-

  • Walking and running– Walking and running are one of the most important uses of friction, without friction we would have simply slided from one place to another without stopping.
  • Driving– Just like friction is needed for walking, while driving also, friction acts between the ground and wheels resulting in forward motion of the vehicle.
  • Application of brakes– To stop any automobile or any moving object, friction is necessary Without friction the object will keep moving like objects in space keep moving due to absence of resisting forces like friction.
  • Climbing– Climbing a slope needs a proper grip to get assistance in forward motion. Without proper grip there are chances of slipping which can lead to serious injuries.
  • Meshing of gears- Gears are nothing but a rough surface, for proper meshing, the gears need to have equal modules so that the teeth can mesh with each other. When the trough of one gear touches the crest of another gear, proper meshing takes place which then helps in translating the motion.

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