Static, kinetic and rolling friction - One Line Questions
1.
The coefficient of kinetic friction between rubber tires and dry asphalt is typically around: —
0.7
2.
If a block of mass 5 kg is at rest on a horizontal surface and the coefficient of static friction is 0.4, what is the minimum force required to start moving it? —
19.6 N
3.
If the coefficient of static friction between a block and a surface is 0.5, and the mass of the block is 10 kg, what is the maximum static friction force? —
49 N
4.
What is the phenomenon where friction causes heat generation at the point of contact? —
Tribology
5.
If a block is at rest on a horizontal surface, the static friction force is: —
Equal to the applied force
6.
If a force F is applied to a block at rest, and the static friction force is f_s, the net force on the block is: —
F - f_s
7.
What is the relationship between the kinetic friction force and the normal force (N)? —
f_k = μ_k N
8.
Which of the following statements about friction is FALSE? —
Friction is a conservative force.
9.
Rolling friction is typically much ______ than kinetic friction. —
smaller
10.
Which of the following is a method to reduce friction? —
Using lubricants
11.
Lubricants reduce friction primarily by: —
Reducing the intermolecular attraction between surfaces
12.
Friction is a non-conservative force because: —
It converts mechanical energy into heat.
13.
A wooden block is pushed across a horizontal wooden table. If the normal force is doubled by placing another identical block on top, how does the kinetic friction change? —
It doubles
14.
What happens to the force of static friction if the applied force is less than the limiting friction? —
It equals the applied force.
15.
The reason why a heavier object experiences more friction than a lighter object (assuming same materials) is: —
It has a greater normal force, leading to greater interlocking of surface irregularities.
16.
Which statement about friction between surfaces is most accurate? —
It depends on the microscopic irregularities of the surfaces.
17.
What is the main advantage of rolling friction over sliding friction in applications like wheels? —
It is significantly smaller, reducing energy loss.
18.
Which type of friction acts when there is no relative motion between the surfaces in contact? —
Static friction
19.
Consider a book resting on a table. If you push it gently and it doesn't move, the friction acting on it is: —
Static friction
20.
Consider a sphere rolling down an inclined plane without slipping. The friction acting between the sphere and the plane is: —
21.
The force required to start moving a stationary object is greater than the force required to keep it moving at a constant velocity because: —
Static friction is greater than kinetic friction.
22.
What is the maximum value of static friction called? —
Limiting friction
23.
Friction is essential for: —
Walking and braking of vehicles
24.
What is the unit of the coefficient of friction? —
No unit (dimensionless)
25.
What is the force that opposes motion or impending motion between surfaces in contact called? —
Friction force
26.
When an object is placed on a surface, the intermolecular forces between the atoms of the two surfaces contribute to: —
Friction
27.
A car tire rolling on a road experiences: —
A combination of static and rolling friction
28.
Which type of friction is most relevant when pushing a box across a floor that is slightly uneven? —
Sliding friction with some deformation
29.
Which type of friction acts when one surface slides over another? —
Kinetic friction
30.
Which type of friction occurs when an object rolls over a surface? —
Rolling friction
31.
If you push the same book harder and it starts to slide, the friction acting on it is now: —
Kinetic friction
32.
A sled is being pulled at a constant velocity across snow. The friction acting on the sled is: —
Kinetic friction
33.
When a fluid (liquid or gas) opposes the motion of an object moving through it, this is called: —
Fluid friction (or drag)
34.
What is the nature of friction when a car's brakes are applied, and the wheels are locked? —
Kinetic friction
35.
Which of the following has the highest coefficient of rolling friction? —
Rubber tire on asphalt
36.
What is the primary cause of friction at the microscopic level? —
Surface roughness and intermolecular attractions
37.
When the angle of inclination of a plane is gradually increased, the block starts to slide when the angle equals: —
The angle of repose
38.
The term 'limiting friction' refers to: —
The maximum possible static friction force.
39.
Which factor does NOT significantly affect the coefficient of kinetic friction for most dry surfaces? —
The area of contact between the surfaces
40.
The force of rolling friction is approximately proportional to: —
The coefficient of rolling friction and the normal force
41.
The force of static friction can vary from zero up to a maximum value. —
True
42.
The coefficient of friction is a dimensionless quantity. —
True
43.
The force of kinetic friction between two surfaces is independent of the velocity, provided the velocity is not too high. —
True
44.
If a block is placed on an inclined plane, the static friction force acts: —
Up the incline
45.
When does kinetic friction become relevant? —
When an object is in motion relative to a surface
46.
When a car's anti-lock braking system (ABS) is active, it aims to keep the friction between the tires and the road as close as possible to: —
The maximum static friction
47.
A block slides down an inclined plane with kinetic friction. If the coefficient of kinetic friction is μ_k, the frictional force is: —
μ_k mg cos θ
48.
The angle of repose (θ) is related to the coefficient of static friction (μ_s) by: —
μ_s = tan θ
49.
The coefficient of static friction (μ_s) is generally related to the coefficient of kinetic friction (μ_k) as: —
μ_s > μ_k
50.
If the coefficient of static friction between two surfaces is μ_s, the minimum horizontal force required to start moving a block of mass m on a horizontal surface is: —
μ_s mg