Friction
Physics ⇒ Mechanics
Friction starts at 8 and continues till grade 12.
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Describe the effect of increasing the normal force on the frictional force between two surfaces.
Describe two methods to reduce friction between two surfaces.
Explain the difference between static friction and kinetic friction.
Explain why ball bearings are used in machines.
A 10 kg box rests on a horizontal surface. If the coefficient of static friction is 0.4, what is the maximum static frictional force that can act on the box? (Take g = 9.8 m/s²)
A 15 kg box is pushed with a force of 100 N on a horizontal surface. If the box moves with constant velocity and the coefficient of kinetic friction is 0.68, what is the normal force acting on the box? (Take g = 10 m/s²)
A 2 kg object is placed on a 30° inclined plane. If the coefficient of static friction is 0.5, will the object slide down? (Take g = 10 m/s²)
A 20 kg crate is at rest on a horizontal floor. The coefficient of static friction is 0.5. What is the minimum horizontal force required to just move the crate? (Take g = 9.8 m/s²)
Which law states that the force of friction is independent of the area of contact? (1) Newton's First Law, (2) Amontons' First Law, (3) Coulomb's Law, (4) Hooke's Law.
Which of the following best defines friction? (1) A force that acts at a distance, (2) A force that opposes the relative motion between two surfaces in contact, (3) A force that acts only on liquids, (4) A force that increases motion between surfaces.
Which of the following does NOT affect the coefficient of friction between two surfaces? (1) The nature of the surfaces, (2) The area of contact, (3) The normal force, (4) The presence of lubricants.
Which of the following is a method to increase friction? (1) Polishing the surfaces, (2) Using lubricants, (3) Making the surfaces rough, (4) Using ball bearings.
The angle of repose is the angle at which an object placed on an inclined plane just begins to slide. It is numerically equal to the arctangent of the ____ of friction.
The force of friction acting on a body is given by F = ____ × N, where N is the normal reaction.
The minimum force required to just move a body at rest on a horizontal surface is called ____ force.
The ratio of the limiting friction to the normal reaction is called the ____ of friction.
True or False: Friction can act when there is no relative motion between two surfaces.
True or False: Friction is a non-conservative force.
True or False: Lubricants increase the coefficient of friction between two surfaces.
True or False: Rolling friction is generally less than sliding friction for the same materials.
