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Chapter 7: Problem 144

Friction force can be reduced to a great extent by a. Lubricating the two moving parts. b. Using ball bearings between two moving parts. c. Introducing a thin cushion of air maintained between two relatively moving surfaces. d. All of the above.

Short Answer

Expert verified
The correct answer is d. All of the above.

Step by step solution

01

Understanding Friction Reduction Methods

To solve this question, we need to review methods used to reduce friction between two moving surfaces. Friction is an opposing force that affects motion when two surfaces slide against each other.
02

Review Each Given Option

Let's evaluate each option to see if it introduces a method for reducing friction: a. Lubricating the two moving parts - Lubrication reduces direct contact between surfaces, thus lowering friction. b. Using ball bearings - Ball bearings reduce friction by replacing sliding motion with rolling motion. c. Introducing a thin cushion of air - Air cushions minimize contact and hence friction between surfaces.
03

Identify the Correct Answer

All options (a, b, c) effectively reduce friction between moving parts by different means: lubrication, rolling contact, and air cushioning. Since each option is valid, option d, 'all of the above', includes all correct methods.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Lubrication: The Slippery Solution
Lubrication involves applying a smooth layer of oil or grease between two surfaces. This layer acts as a buffer preventing the surfaces from grinding directly against each other.
Lubrication is crucial because it reduces the friction that occurs when two objects slide past one another. The effectiveness of lubrication stems from its ability to create a film between surfaces, which mitigates direct metal-to-metal contact. It minimizes the wear and tear of the moving parts.
  • Reduces heat generation
  • Lowers energy consumption
  • Extends the lifespan of machinery
Different lubricants are used depending on the machinery, from lightweight oils to heavy-duty greases.
Ball Bearings: From Sliding to Rolling
Ball bearings are tiny spherical components strategically placed between moving parts. Their main function is to change sliding friction into much gentler rolling friction.
The magic of ball bearings lies in their shape. When placed between two surfaces, they roll rather than slide. This reduces the frictional force immensely. The smooth spherical balls ensure a steady and balanced motion, sparing machinery from excessive friction.
  • Provides smooth motion
  • Prevents excessive wear
  • Handles high loads efficiently
Industries rely heavily on ball bearings to enhance the efficiency and durability of machines.
Air Cushioning: Floating on Air
Air cushioning is an innovative approach to minimize friction by creating a thin layer of air between two surfaces. This is particularly fascinating as it almost makes parts "float" above each other.
By pumping air between surfaces, direct contact is avoided, thus significantly reducing friction. It acts like a cushion, distributing pressure evenly and allowing smoother movement. Air mattresses and hovercrafts are examples where air cushioning aids in reducing friction effectively.
  • Non-contact movement
  • Minimal maintenance requirement
  • Highly efficient for lightweight applications
It's a cutting-edge technique which allows for almost frictionless movement in various devices.

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Most popular questions from this chapter

A block of metal weighing \(2 \mathrm{~kg}\) is resting on a frictionless plane. It is struck by a jet releasing water at a rate of 1 \(\mathrm{kg} / \mathrm{s}\) and a speed of \(5 \mathrm{~m} / \mathrm{s}\). The initial acceleration of the block will be a. \(2.5 \mathrm{~m} / \mathrm{s}^{2}\) b. \(5 \mathrm{~m} / \mathrm{s}^{2}\) c. \(10 \mathrm{~m} / \mathrm{s}^{2}\) d. \(20 \mathrm{~m} / \mathrm{s}^{2}\)

Two persons are holding a rope of negligible weight tightly at its ends so that it is horizontal. A \(15 \mathrm{~kg}\) weight in attached to rope at the mid point which now no more remains horizontal. The minimum tension required to completely straighten the rope is a. \(150 \mathrm{~N}\) b. \(75 \mathrm{~N}\) c. \(50 \mathrm{~N}\) d. infinitely large

Three light strings are connected at the point \(P .\) A weight \(W\) is suspended from one of the strings. End \(A\) of string AP and end \(B\) of string \(P B\) are fixed as shown. In equilibrium \(P B\) is horizontal and \(P A\) makes an angle of \(60^{\circ}\) with the horizontal. If the tension in \(P B\) is \(30 \mathrm{~N}\) then the tension in \(P A\) and weight \(W\) are respectively given by a. \(60 \mathrm{~N} ; 30 \mathrm{~N}\) b. \(60 / \sqrt{3} \mathrm{~N} ; 30 / \sqrt{3} \mathrm{~N}\) c. \(60 \mathrm{~N} ; 30 \sqrt{3} \mathrm{~N}\) d. \(60 \sqrt{3} \mathrm{~N}: 30 \sqrt{3} \mathrm{~N}\)

A particle of small mass \(m\) is joined to a very heavy body by a light string passing over a light pulley. Both bodies are free to move. The total downward force on the pulley is a. \(>>m g\) b. \(4 \mathrm{mg}\) c. \(2 \mathrm{mg}\) d. \(\overline{m g}\)

\(n\) balls each of mass \(m\) impinge elastically each second on a surface with velocity \(u\). The average force experienced by the surface will be a. \(\mathrm{mu}\) b. \(2 \mathrm{mnu}\) c. \(4 \mathrm{~mm}\) d. mnu/2
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