Which of the following option is CORRECT about the methods used to reduce the friction?
Use of lubricants
Understanding Friction and Its Reduction
Friction is a force that opposes motion between two surfaces that are in contact with each other. While friction can be useful (like helping us walk without slipping), it often causes wear and tear and wastes energy. Therefore, reducing friction is important in many situations, such as in machines.
Methods to Reduce Friction: Analyzing Options
Let's examine the given options to determine which one describes a method used to reduce friction:
- Option 1: Making a rough surface
Making a surface rough actually increases friction. Rough surfaces have more irregularities that interlock, opposing motion more effectively. So, this option is incorrect.
- Option 2: Use of lubricants
Lubricants, such as oil, grease, or even graphite, are substances applied between two surfaces in contact. They form a thin layer that separates the surfaces, allowing them to slide over each other more easily. This significantly reduces the friction between the surfaces. This is a common and effective method for reducing friction in engines, hinges, and other moving parts.
- Option 3: Use of sand particles
Using sand particles between surfaces would make the surfaces much rougher. Sand particles act like tiny irregular bumps, greatly increasing friction. Sand is sometimes used to *increase* friction, for example, spread on icy roads or railway tracks to improve grip. So, this option is incorrect.
- Option 4: None of these
Since Option 2 correctly identifies a method for reducing friction, this option is incorrect.
Why Lubricants Reduce Friction
When a lubricant is used between two surfaces, it fills the microscopic gaps and irregularities on both surfaces. Instead of the solid surfaces directly rubbing against each other, they slide over the thin layer of lubricant. The friction within the lubricant layer itself (viscosity) is much lower than the friction between the solid surfaces. This leads to a significant reduction in the overall frictional force opposing motion.
Therefore, the use of lubricants is a correct method for reducing friction between surfaces.
Important Questions from Friction
A steel wheel of 600 mm diameter rolls on a horizontal steel rail. It carries a load of 500 N. The coefficient of rolling resistance is 0.3 mm. The force in N, necessary to roll the wheel along the rail is:
Which of the following is NOT a law of static friction?
If we push the break of car then car will begin to slide when:
An elephant is stopped by a rope wound twice around the rough trunk of a tree. If the elephant exerts a pull of 1000 kgf, the minimum force required to stop the elephant is_________. (Coefficient of friction between the rope and the tree is 0.3)
A block of mass 20 Kg is placed on a horizontal surface. Co-efficient of static friction and coefficient of kinematic friction between the block and surface are 0.5 and 0.4 respectively. What is the minimum force required to be applied on the block in horizontal direction so that the block just starts to move. Consider g = 10 m/sec2.
