Friction Practice Questions
18 free Friction practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is friction?
- A A force that opposes relative motion between surfaces in contact
- B A force that pulls all objects steadily downward toward Earth's center
- C The heat energy that is released when two surfaces rub together
- D The natural tendency of an object to resist a change in its motion
Correct answer: A force that opposes relative motion between surfaces in contact
Friction is a contact force that opposes the relative motion or tendency of motion between two surfaces. It acts along the surfaces in contact.
In which direction does friction act on a sliding object?
- A In the same direction as the object's motion.
- B Vertically upward, away from the surface.
- C Toward the center of the Earth.
- D Opposite to the direction of relative motion.
Correct answer: Opposite to the direction of relative motion.
Friction acts opposite to the direction of relative motion between surfaces. This is why a sliding object gradually slows down.
Which of the following surfaces generally produces the greatest friction?
- A Polished glass
- B Wet ice
- C Rough concrete
- D Smooth plastic
Correct answer: Rough concrete
Rough concrete has many irregularities that interlock with another surface. This increases friction compared with smoother surfaces.
Which type of friction acts when an object is at rest but tends to start moving?
- A Static friction
- B Sliding friction
- C Rolling friction
- D Fluid friction
Correct answer: Static friction
Static friction acts between surfaces when there is no actual sliding motion. It prevents an object from starting to move until the applied force becomes large enough.
Which type of friction acts when one solid surface slides over another?
- A Static friction
- B Magnetic friction
- C Gravitational friction
- D Sliding friction
Correct answer: Sliding friction
Sliding friction acts when two surfaces slide against each other. It is usually less than maximum static friction but greater than rolling friction.
Which type of friction acts when a wheel rolls over a surface?
- A Rolling friction
- B Sliding friction
- C Static electricity
- D Buoyant force
Correct answer: Rolling friction
Rolling friction acts when an object rolls over a surface. It is generally much smaller than sliding friction, which is why wheels make movement easier.
Why are wheels used in vehicles?
- A They replace sliding friction with much smaller rolling friction
- B They reduce the vehicle's overall gravitational pull on the road
- C They increase the sliding friction between the road and axle
- D They bring a fast-moving vehicle to a complete stop instantly
Correct answer: They replace sliding friction with much smaller rolling friction
Wheels reduce the effort needed to move vehicles by changing sliding motion into rolling motion. Rolling friction is much less than sliding friction.
Which of the following is used to reduce friction in machines?
- A Lubricants
- B Sand
- C Rough stones
- D Dry mud
Correct answer: Lubricants
Lubricants such as oil and grease form a thin layer between moving parts. This reduces direct contact and lowers friction.
How do ball bearings reduce friction?
- A By changing sliding friction into much smaller rolling friction
- B By increasing the roughness between the two contacting surfaces
- C By removing most of the weight resting on the moving part
- D By converting frictional heat directly into visible light
Correct answer: By changing sliding friction into much smaller rolling friction
Ball bearings allow parts to roll over small balls instead of sliding directly. Since rolling friction is less than sliding friction, the motion becomes smoother.
Which of the following is a disadvantage of friction?
- A It helps us walk safely on rough ground without slipping.
- B It allows for controlled writing with a simple pencil.
- C It causes wear and tear of the machine's parts over time.
- D It helps vehicles stop safely at busy traffic signals.
Correct answer: It causes wear and tear of the machine's parts over time.
Friction between moving parts can cause wear and tear over time. It may also produce unwanted heat and reduce efficiency.
Which of the following is an advantage of friction?
- A It wastes energy as heat in every single machine.
- B It prevents a pen's ink from marking the paper.
- C It makes ordinary walking on flat ground impossible.
- D It helps brake pads grip and stop a moving vehicle.
Correct answer: It helps brake pads grip and stop a moving vehicle.
Friction between brake pads and wheels helps slow down or stop a vehicle. Without friction, braking would not be effective.
Why are tyres provided with treads?
- A To make the outer surface of the tyre completely smooth.
- B To reduce the vehicle's total mass down toward zero.
- C To increase the grip and friction between tyre and road.
- D To stop outside air from ever entering the tyre.
Correct answer: To increase the grip and friction between tyre and road.
Treads increase friction between tyres and the road surface. They are especially useful on wet roads because they help reduce slipping.
Friction between a moving object and air is called:
- A Magnetic force
- B Static charge
- C Air resistance
- D Elastic force
Correct answer: Air resistance
Air resistance is a type of fluid friction that opposes motion through air. It becomes more significant at higher speeds.
Which shape helps reduce fluid friction for fast-moving vehicles?
- A Irregular shape
- B Flat broad shape only
- C Streamlined shape
- D Rough square shape
Correct answer: Streamlined shape
A streamlined shape allows air or water to flow smoothly around an object. This reduces fluid friction or drag.
Why do athletes wear spiked shoes on a track?
- A To increase friction with the ground
- B To reduce oxygen intake
- C To make shoes slippery
- D To eliminate the pull of gravity during a sprint
Correct answer: To increase friction with the ground
Spikes dig into the track surface and increase friction. This gives athletes better grip while running.
What usually happens when friction acts between two surfaces for a long time?
- A Heat may be produced
- B Gravity disappears
- C The surfaces become invisible
- D Mass is created from nothing
Correct answer: Heat may be produced
Friction converts some mechanical energy into heat energy. This is why rubbing hands together makes them feel warm.
Which factor generally increases friction between two solid surfaces?
- A Greater roughness of surfaces
- B Adding oil between surfaces
- C Making surfaces perfectly smooth
- D Using ball bearings
Correct answer: Greater roughness of surfaces
Rough surfaces have more irregularities that interlock with each other. This usually increases friction compared with smoother surfaces.
Why is friction called a necessary evil?
- A It helps daily activities but causes wear and energy loss
- B It is never useful in daily life
- C It exists only in machines and factories
- D It always increases the speed of every moving object it touches instantly
Correct answer: It helps daily activities but causes wear and energy loss
Friction is necessary for walking, writing, gripping, and braking. However, it also causes wear, heat production, and loss of useful energy, so it is called a necessary evil.