MCQ (Solution) - Friction | Science Class 8 PDF Download

Q1: What is the force that opposes motion between surfaces in contact with each other?
(a) Tension force
(b) Frictional force
(c) Gravitational force
(d) Magnetic force

Correct Answer is Option (b)
The force that opposes motion between surfaces in contact with each other is called friction. Friction is a force that acts at the interface between two objects in contact and resists their relative motion. It is caused by the irregularities and roughness of the surfaces in contact.Friction

Q2: Which factor directly affects the magnitude of friction by being proportional to the frictional force? 
(a) Temperature 
(b) Normal force 
(c) Lubrication 
(d) Relative speed 

Correct Answer is Option (b)
The factor that directly affects the magnitude of friction by being proportional to the frictional force is the normal force. The normal force is the force exerted by a surface that is perpendicular to the surface. In the context of friction, it is the force exerted by a surface that is perpendicular to the object pressing against it. 

Q3: Why does walking on a rough road create more friction than walking on a polished floor? 
(a)Rough roads generate more heat 
(b) Irregularities on rough surfaces interlock, creating more resistance 
(c) Polished floors increase the normal force 
(d) Polished floors have higher coefficients of friction 

Correct Answer is Option (b)
Walking on a rough road creates more friction than walking on a polished floor primarily due to differences in the surface roughness and irregularities of the materials. Friction is the force that opposes motion between surfaces in contact, and it depends on the nature of the surfaces in contact. Walking on Road

Q4: What effect does the presence of lubricants, such as oil or grease, have on friction between two surfaces? 
(a) Increases friction 
(b) No impact on friction 
(c) Reduces friction 
(d) Changes the type of friction 

Correct Answer is Option (c)
The presence of lubricants, such as oil or grease, has a significant effect on friction between two surfaces. Lubricants are substances that are applied to surfaces in contact to reduce friction and wear. They work by forming a thin film or layer between the surfaces, altering the nature of their interaction. Engine Oiling

Q5: Which material typically has a higher coefficient of friction on most surfaces compared to plastic or metal? 
(a) Metal 
(b) Plastic 
(c) Rubber 
(d)  Glass 

Correct Answer is Option (c)
While the coefficient of friction can vary depending on specific materials, in general, rubber typically has a higher coefficient of friction on most surfaces compared to plastic or metal. Rubber is known for its high coefficient of friction due to its elastic and tacky nature. Rubber Tires

Q6: What is the primary purpose of the treads on vehicle tires? 
(a) Enhance aesthetics 
(b) Reduce weight 
(c)  Improve grip and friction with the road surface 
(d) Increase fuel efficiency 

Correct Answer is Option (c)
The primary purpose of the treads on vehicle tires is to provide traction and improve overall performance in various road conditions. Treads are the patterned grooves and channels on the surface of a tire that come into direct contact with the road.  Treaded Tires

Q7: In which scenario does an increase in temperature generally reduce friction? 
(a) Lubrication 
(b) Sliding on ice 
(c) Using sandpaper 
(d) Rubber on a rough road 

Correct Answer is Option (a)
An increase in temperature generally reduces friction in scenarios involving sliding friction, also known as kinetic friction. This behavior is often observed in systems where lubrication is involved. When the temperature increases, it can lead to changes in the viscosity of lubricating fluids, causing them to become less viscous or more fluid. 

Q8: What type of friction occurs between objects when they are resting on a surface? 
(a)  Sliding friction 
(b) Rolling friction 
(c) Static friction 
(d) Fluid friction 

Correct Answer is Option (c)
The type of friction that occurs between objects when they are resting on a surface and are not in motion is called static friction. Static friction is the force that prevents two objects from sliding past each other when they are at rest relative to each other. 

Q9: How does smoothing or polishing surfaces contribute to reducing friction? 
(a)  It increases irregularities 
(b)  It enhances heat generation 
(c)  It minimizes surface roughness 
(d) It strengthens the normal force 

Correct Answer is Option (c)
Smoothing or polishing surfaces contributes to reducing friction primarily by minimizing surface irregularities and promoting smoother interactions between the two surfaces. 

Q10: What is the primary purpose of the streamlined shape in objects moving through fluids? 
(a)  To increase friction 
(b) To generate heat 
(c) To reduce air resistance and fluid friction 
(d)  To enhance aesthetic appeal 

Correct Answer is Option (c)
The primary purpose of a streamlined or aerodynamic shape in objects moving through fluids (such as air or water) is to reduce drag, increase efficiency, and improve overall performance. This shape is designed to minimize resistance as the object moves through the fluid, whether it's an aircraft, a vehicle, or an underwater object. Fighter Jet