Friction — Set 3
Physics · घर्षण · Questions 21–30 of 60
Which shape is most effective in reducing fluid friction?
Correct Answer: A. Streamlined
A streamlined shape is designed to allow fluids to flow smoothly around an object with minimal resistance. Nature provides examples of this in the shapes of fish and birds. Engineers use this principle to design fast cars and airplanes.
Which of the following is a disadvantage of friction?
Correct Answer: B. It causes noise
Friction causes noise as energy is converted into sound vibrations during the rubbing of parts. In many machines, this noise is an unwanted sign of energy inefficiency. Excessive noise can also indicate that the parts need lubrication.
What happens if we apply grease to the chain of a bicycle?
Correct Answer: B. Friction decreases
Applying grease reduces friction by providing a smooth lubricating layer between the metal links of the chain. This makes the pedaling easier and reduces the wear and tear of the chain. Lubrication is vital for the smooth operation of most mechanical systems.
Static friction is always _____ kinetic friction for the same set of surfaces.?
Correct Answer: D. Greater than
Static friction is greater than kinetic friction because more force is needed to break the initial interlocking of surfaces. Once the object is in motion, the irregularities do not have enough time to interlock as deeply. This is why it is harder to start moving a heavy box than to keep it moving.
The use of talcum powder on a carrom board is intended to _____.?
Correct Answer: C. Reduce friction
Talcum powder reduces friction by filling the tiny pits and irregularities on the carrom board surface. This allows the coins and the striker to slide more smoothly and travel longer distances. It is a common household example of using a solid lubricant.
Which of the following is NOT a type of friction?
Correct Answer: C. Centripetal friction
Centripetal friction is not a standard category of friction in physics. Static, rolling, and sliding (kinetic) are the primary types of dry friction. Centripetal refers to a direction of force toward a center, not the nature of the resistance.
In which medium is fluid friction (drag) generally higher?
Correct Answer: D. Water
Fluid friction is higher in water than in air because water is much denser and more viscous. Objects moving through water experience significantly more resistance than those moving through air. Viscosity is a measure of a fluid's internal resistance to flow.
Why do athletes wear shoes with spikes?
Correct Answer: C. To increase friction
Spikes increase friction by digging into the ground, providing a very strong grip for the athlete. This extra traction allows for faster starts and prevents slipping during high-speed running. Spiked shoes are essential for sports like track and field or football.
When two surfaces are separated by a layer of air, the friction _____.?
Correct Answer: A. Decreases significantly
Separating surfaces with a layer of air decreases friction significantly as air has very low viscosity. This principle is used in hovercrafts and air-hockey tables to achieve near-frictionless motion. Air bearings are used in high-precision machinery to minimize wear.
Friction converts mechanical energy into which form of energy?
Correct Answer: D. Heat energy
Friction converts the kinetic energy of motion into heat energy through the interaction of surface molecules. This is why mechanical parts get hot after prolonged use. In some cases, this conversion can also produce light or sound.