Friction: Master the Fundamentals for Engineering Mechanics

Question 1

Which of the following is the definition of the coefficient of friction?

Accepted Answer

The ratio of the force of friction to the normal force

Answer

The ratio of the normal force to the force of friction

Answer

The tangent of the angle of friction

Answer

The cosine of the angle of friction

Question 2

A block is resting on a horizontal surface. The coefficient of friction between the block and the surface is 0.5. What is the minimum angle of inclination required to start the block moving?

Accepted Answer

26.5°

Answer

30°

Answer

45°

Answer

60°

Question 3

Which of the following factors does NOT affect the force of friction?

Accepted Answer

Humidity

Answer

Normal force

Answer

Coefficient of friction

Answer

Surface roughness

Question 4

Which of the following lubricants reduces friction primarily by forming a film between two surfaces?

Accepted Answer

Teflon

Answer

Graphite

Answer

Molybdenum disulfide

Answer

Water

Question 5

According to Amontons' first law of friction, the force of friction is:

Accepted Answer

Proportional to the normal force

Answer

Independent of the contact area

Answer

Equal to the force applied parallel to the surface

Answer

Zero when the object is stationary

Question 6

Which of the following is NOT a valid application of friction?

Accepted Answer

Improving traction on wet roads

Answer

Brakes in vehicles

Answer

Clutches in machinery

Answer

Bearings in rotating shafts

Question 7

The static coefficient of friction is:

Accepted Answer

Greater than the kinetic coefficient of friction

Answer

Equal to the kinetic coefficient of friction

Answer

Less than the kinetic coefficient of friction

Answer

Zero when the object is at rest

Question 8

A wedge is used to lift a heavy object. The mechanical advantage of the wedge is determined by:

Accepted Answer

Length of the wedge / Height of the wedge

Answer

Height of the wedge / Length of the wedge

Answer

Width of the wedge / Height of the wedge

Answer

Height of the wedge / Width of the wedge

Question 9

The coefficient of friction is a dimensionless quantity that measures:

Accepted Answer

The ratio of the force of friction to the normal force

Answer

The roughness of the surfaces in contact

Answer

The force required to overcome friction

Answer

The angle of inclination at which an object begins to slide

Question 10

Which of the following factors **DOES NOT** affect the coefficient of friction?

Accepted Answer

Contact area

Answer

Surface roughness

Answer

Material properties

Answer

Temperature

Question 11

A block of mass 'm' is resting on a horizontal surface with a coefficient of friction 'μ'. The minimum force required to start the block moving is:

Accepted Answer

μmg

Answer

mg/μ

Answer

μ/mg

Answer

(μm)g

Question 12

Rolling friction is generally:

Accepted Answer

Lower than sliding friction

Answer

Higher than sliding friction

Answer

Equal to sliding friction

Answer

Independent of the type of surface

Question 13

Identify and briefly describe the three main types of friction.

Accepted Answer

Static, Kinetic, and Rolling

Answer

Sliding, Rolling, and Pivoting

Answer

Coulomb, Viscous, and Fluid

Answer

Dry, Wet, and Mixed

Question 14

Which of the following statements about friction is **incorrect**?

Accepted Answer

Static friction is always greater than or equal to kinetic friction.

Answer

The coefficient of friction is a dimensionless quantity.

Answer

Friction always opposes the potential relative motion between two surfaces in contact.

Question 15

Which of the following is the correct expression for the force of friction (Ff) between two surfaces, where μ is the coefficient of friction and N is the normal force?

Accepted Answer

Ff = μ * N

Answer

Ff = N / μ

Answer

Ff = μ / N

Question 16

Which type of friction occurs when two surfaces are momentarily stationary relative to each other?

Accepted Answer

Static friction

Answer

Kinetic friction

Answer

Rolling friction

Answer

Fluid friction

Question 17

Which of the following actions would lead to an increase in the coefficient of friction?

Accepted Answer

Roughening the surfaces

Answer

Reducing the normal force

Answer

Increasing the surface area

Answer

Applying a lubricant

Question 18

What is the relationship between the coefficients of static friction (μs) and kinetic friction (μk)?

Accepted Answer

Typically, μs > μk

Answer

μs = μk

Answer

μs < μk

Answer

μs is unrelated to μk

Question 19

Which of the following statements accurately describes friction?

Accepted Answer

Friction is a force that opposes relative motion between surfaces in contact.

Answer

The force of friction is independent of the surface area in contact.

Answer

Friction can be completely eliminated in practical systems.

Answer

Friction is always beneficial in engineering applications.

Question 20

A 2 kg block is at rest on a horizontal surface. The coefficient of static friction between the block and the surface is 0.4. Calculate the minimum horizontal force required to move the block.

Accepted Answer

7.84 N

Answer

0 N

Answer

3.92 N

Answer

19.6 N

Question 21

Which of the following statements correctly describes the coefficient of friction?

Accepted Answer

It is a dimensionless quantity.

Answer

It depends on the surface roughness.

Answer

It is always constant for a given pair of materials in contact.

Answer

It is always greater than 1.

Question 22

A car travels at a constant velocity on a level road. What is the relationship between the driving force and the frictional force acting on the car?

Accepted Answer

The driving force is equal in magnitude but opposite in direction to the frictional force.

Answer

The driving force is greater than the frictional force.

Answer

The driving force is less than the frictional force.

Question 23

Which type of friction is primarily responsible for the wear and tear of moving parts in machinery?

Accepted Answer

Kinetic friction

Answer

Static friction

Answer

Rolling friction

Question 24

How does lubrication reduce friction between two surfaces in contact?

Accepted Answer

By introducing a fluid layer that separates the surfaces, reducing the shearing force.

Answer

By increasing the surface roughness.

Answer

By increasing the normal force between the surfaces.

Question 25

A block slides down an inclined plane at a constant velocity. What is the relationship between the coefficient of kinetic friction between the block and the plane and the angle of inclination?

Accepted Answer

The coefficient of kinetic friction is equal to the tangent of the angle of inclination.

Answer

The coefficient of kinetic friction is greater than the tangent of the angle of inclination.

Answer

The coefficient of kinetic friction is less than the tangent of the angle of inclination.

Question 26

During braking, a car's braking system utilizes friction to convert kinetic energy into which form of energy?

Accepted Answer

Heat energy

Answer

Potential energy

Answer

Electrical energy

Answer

Chemical energy