Chapter 10 : Principles of Lifting Machines „„„„„ 171

171

Principles of

Lifting Machines

Contents

1. Introduction.


2. Simple Machine.


3. Compound Machine.


4. Lifting Machine.


5. Mechanical Advantage.


6. Input of a Machine.


7. Output of a Machine.


8. Efficiency of a Machine.


9. Ideal Machine.


10. Velocity Ratio.


11. Relation Between
    Efficiency, Mechanical
    Advantage and Velocity
    Ratio of a Lifting Machine.


12. Reversibility of a Machine.


13. Condition for the
    Reversibility of a Machine.


14. Self-locking Machine.


15. Friction in a Machine.


16. Law of a Machine.


17. Maximum Mechanical
    Advantage of a Lifting
    Machine.


18. Maximum Efficiency of a
    Lifting Machine.

10.1. INTRODUCTION

In olden times, thousands of slaves had to be

arranged, whenever a heavy load had to be lifted or

dragged. Even today, in the absence of a suitable

device, many people have to be arranged to lift a motor

car so that its tyres can be changed. In order to

overcome such difficulties, a few simple machines were

invented, which could save the man power i.e., a single

man can do the same work as many could do, though

at a lesser speed.

Before entering into the details of simple

machines and their working, following terms should

be clearly understood at this stage :

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