Friction — Set 1
Physics · घर्षण · Questions 1–10 of 60
Which type of friction occurs between two surfaces that are not moving relative to each other?
Correct Answer: D. Static friction
Static friction is the force that prevents an object from starting to move on a surface. It is generally the strongest type of friction between two solid surfaces. This force must be overcome for an object to begin its motion.
What happens to the frictional force when the roughness of the surfaces in contact increases?
Correct Answer: A. It increases
Frictional force increases when the surfaces in contact are rougher due to more interlocking of irregularities. These microscopic peaks and valleys create resistance against relative motion. Smooth surfaces typically experience much lower frictional resistance.
Which of the following is used to reduce friction in rotating machine parts?
Correct Answer: A. Ball bearings
Ball bearings reduce friction by converting sliding motion into rolling motion. Rolling friction is significantly less than sliding friction for most materials. This technology is widely used in bicycle wheels and fans.
Friction is a force that always acts in which direction relative to the motion?
Correct Answer: D. Opposite direction
Friction always acts in the opposite direction to the relative motion of an object. It works to resist or slow down the movement of the surfaces. Without this resistance, objects would never stop moving once started.
Which of the following substances acts as a lubricant to reduce friction?
Correct Answer: C. Oil
Oil acts as a lubricant by creating a thin layer between the moving surfaces. This layer prevents direct contact between the microscopic irregularities of the surfaces. Graphite is another common solid lubricant used in machinery.
The friction experienced by an object moving through a liquid or gas is called _____.?
Correct Answer: D. Drag
Drag is the frictional force exerted by fluids like air or water on a moving object. The shape of an object greatly affects the amount of drag it experiences. Airplanes are streamlined to minimize this specific type of friction.
Why is it difficult to walk on a wet marble floor?
Correct Answer: B. Friction decreases
Water on the floor acts as a lubricant and significantly decreases the friction. Reduced friction makes it harder for our feet to get a firm grip on the ground. Walking requires a certain amount of friction to prevent slipping.
Which of the following parts of a shoe is designed to increase friction with the ground?
Correct Answer: D. Sole
The sole of a shoe is often grooved or textured to increase friction with the walking surface. This design provides better grip and prevents the person from slipping. Different sports require specific sole patterns for optimal traction.
When a book slides on a table, the friction produced is known as _____.?
Correct Answer: B. Kinetic friction
Kinetic friction, also called sliding friction, occurs when two surfaces move relative to each other. This force is usually slightly less than the maximum static friction for the same surfaces. It is responsible for generating heat during sliding motion.
Which force is responsible for the wear and tear of machine parts?
Correct Answer: D. Frictional force
Frictional force causes the surfaces of machine parts to rub against each other and wear out. Over time, this constant contact leads to the erosion of material from the parts. Regular maintenance and lubrication help in extending the life of these components.