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Friction is defined as the force that prevents motion when the surfaces of two objects come into contact.
- As two solid surfaces, fluid layers, and material components slide past one another, friction acts as a stopping force to prevent the motion or tendency of the relative motion.
- Microscopic observations show that surface irregularities are the cause of friction.
- Example: When a ball is thrown on the ground, it begins to travel with some velocity.
- According to Newton's first law, the ball should continue to roll if no force is applied in the direction of motion, however, this does not occur.
- The frictional force that exists between two surfaces of substances when they are not moving relative to one another is known as static friction.
- Limiting friction is the amount of static friction that one body can apply to another body in contact with it.
- Kinetic friction is the frictional force that opposes an object's motion and is not changed by velocity.
Ques. Define the force of friction.
Ans. The force of friction or frictional force is defined as the force that resists the motion of one body over another in contact with it.
Ques. What is the cause of friction?
Ans. The frictional force is caused by molecule adhesion, surface roughness, and deformations. Adhesion is the molecular force that occurs when two materials come into close contact with each other.
Ques. What is sliding friction?
Ans. Sliding friction, sometimes referred to as moving friction or kinetic friction, is the force needed to keep one surface moving over another surface.
Ques. Give some examples of sliding friction.
Ans. Examples of sliding friction are
- A mat is sliding against a table.
- A car is sliding on ice.
- A washing machine is being pushed along with the floor.
- A child is sliding through a slide in a park.
Ques. What is static friction?
Ans. A force that holds an object at rest is called static friction. It is defined as the friction that individuals feel when they attempt to move a stationary object over a surface without actually causing any relative motion between their body and the surface.
Ques. Give some examples of static friction.
Ans. Examples of static friction are
- A car parked on a hill.
- Papers on a tabletop.
- A bookmark in a book.
- A towel hanging on a rack.
Ques. Define the coefficient of friction.
Ans. A constant ratio occurs at the surface of contact between two bodies; this ratio is known as the coefficient of friction. It is defined as the frictional force divided by the normal reaction on a surface.
Ques. What is the coefficient of static friction?
Ans. The maximum ratio of applied force to normal force when there is no motion is known as the coefficient of static friction.
Ques. Give the formula for the coefficient of static friction.
Ans. The coefficient of static friction is given by the formula
µs = Fs/FN
Where
- µs is the coefficient of static friction
- Fs is the static friction or maximum applied force
- FN is the normal force
Ques. What is limiting friction?
Ans. Limiting friction is the friction that develops between two static surfaces when they come into contact. It is the product of the normal force and the coefficient of limiting friction.
Ques. Give some examples of limiting the force of friction.
Ans. Examples of limiting friction include
- Moving a car on a cliff.
- Moving an object on the ground.
- Walking on the road.
Ques. What is the coefficient of limiting friction?
Ans. Normal reaction directly relates to the amount of limiting friction. Therefore, the ratio of limiting friction to the normal reaction is known as the coefficient of limiting friction.
Ques. Give the formula for the coefficient of limiting friction.
Ans. The coefficient of limiting friction is given by the formula
µL = FL/FN
Where
- µL is the coefficient of static friction
- FL is the limiting friction
- FN is the normal force
Ques. The coefficient of static friction is more than the coefficient of kinetic friction. Is it true or false?
Ans. Because the normal reaction between two surfaces is directly proportional to the amount of kinetic energy, therefore, the static friction coefficient is greater than the kinetic friction coefficient. The statement in question is true.
Ques. How can one reduce the friction due to air?
Ans. The friction caused by air may be considerably decreased by streamlining the shape of the body moving through it, as seen in the streamlined shapes of jets and fins of airplanes.
Ques. What is kinetic friction?
Ans. When two or more bodies are in touch and moving relative to one another, a physical phenomenon called kinetic friction occurs that consumes energy and wears down objects.
Ques. How many types of kinetic friction are there?
Ans. Rolling friction and sliding friction are the two types of kinetic friction. Due to the fact that sliding friction is greater than rolling friction, rolling a body is always easier than sliding.
Ques. Why are brake surfaces kept flat?
Ans. When the brakes are applied, they are pushed away from the surface of the brake rotor and the hydraulic pistons. Because brakes are always applied from both sides, causing friction and causing the car to stop, the surface of the brakes should be kept flat to achieve maximum friction.
Ques. After rain, the roads become slippery; why?
Ans. When it rains, a thin layer of moisture covers the road's surface, reducing friction between the feet and the road. As a result, when it rains, the roadways become slippery.
Ques. Is it possible to have zero friction?
Ans. No, zero friction surfaces are not possible. Even if we use a lot of lubricants, friction will be minimized, but it will never be zero since every surface has minor irregularities.
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