Simple Machine

Published by: BhumiRaj Timalsina

Published Date: 24 Jan 2022

Simple Machine in Grade-7 Reference Note

Introduction

We use various types of machine in our daily life to perform various activities. These machines make our work easy and efficient. For example, we use a knife to chop vegetables, scissors to cut papers, beam balance to measure weight, bottle opener to open the bottle, etc. There are a simple machine and complex machine. Forceps, punching machine, crowbar, bottle opener, etc. are examples of the simple machine while motorcycle, truck, car, etc. are some examples of the complex machine. A simple machine is a device, which is simple in structure and makes our daily work easier, faster and more convenient.

Types of Simple Machines

Mainly, there are six types of simple machines, which are given below,

  • Lever
  • Wheel and axle
  • Screw
  • Pulley
  • Inclined plane
  • Wedge

 

Lever

Lever is a type of simple machine that is used to lift the heavy loads. It is made of a rigid bar that moves about a fixed point called fulcrum. It consists of three parts, effort arm, fulcrum and load arm. Fulcrum is the point where rigid bar rotates. By applying effort in effort arm the load is lifted by the help of fulcrum. Effort arm is the distance between the fulcrum and the point where effort is applied and load arm is the distance between fulcrum and load where the load is kept. Input work is equal to output work in an ideal lever which is the balanced condition of the lever. It is the principle of the lever.
Levers are of three types depending upon the positions of fulcrum, load, and effort which are as follows,

 

  1. First class lever: In the first class lever, fulcrum lies between effort and the load. Effort arm is longer than load arm. Beam balance, scissors, crowbar, etc are some examples of the first class lever.
  2. Second class lever: In the second class lever, the load is placed between the fulcrum and the effort. Since effort arm is longer than load arm it multiplies the applied effort which helps to lift the heavy load by applying small effort. Wheel-barrow, nut- cracker, paper- cutter, etc. are some examples of the second class lever.
  3. Third class lever: In the third class lever, the effort is located in between fulcrum and load. Here, effort arm is shorter than the load arm. It cannot lift the heavy load but increases the speed of doing work. Fire tongs, fishing rod, shovel, etc. are the examples of the third class lever.

Pulley

A pulley is a simple machine consisting grooved circular disc and a rope. The rope passes over the circular disc. In pulley, a load is attached to one end of the rope while the effort is applied at the another end of the same rope. Here, the effort is applied in a convenient way which makes our work easier. There are two types of the pulley on the basis of their movements. They are as follows,

  1. Fixed pulley: In fixed pulley, the pulley remains in the same position or fixed at the point while the pulley’s wheel moves with the rope that passes through it while raising the load. It is used to lift water from well. It is also used in flag poles.
  2. Movable pulley: In movable pulley, the pulley moves with the load. Both load and pulley move upward when the rope is moved upward. One end of the rope is fixed at one point and effort is applied to another point. Here, applied effort is equally shared by both parts of the rope due to which we can lift the load two times heavier than the applied effort. For example, we can uplift the load of 20N by applying 10N effort.

 

Wheel and axle

It consists of two cylinders having a different radius. Cylinder with a small radius is axle and cylinder with a large radius is a wheel. Formally, a rope is coiled in wheel and axle. The effort is applied in wheel and load in the axle. They move in the same manner but the distance covered is different due to the difference in radius. Since effort applied on the wheel is magnified so, by applying small effort on the wheel, heavy loads can be lifted. Some of the examples of wheel and axle are paddle of the bicycle, a drill used by carpenters, steering of vehicles, etc.

Source: bvg8science.wikispaces.com Fig: Wheel and Axle

 

 

Inclined plane

It is very difficult to load heavy things onto a truck or some area of a certain height. A huge effort is needed. In such case, the inclined plane is used. It is a sloping surface or a wooden plank. It multiplies the applied effort. It helps to push the heavy load upward easily. The winding road, staircase, ladder, etc. are the examples of an inclined plane.

Source: socratic.org Fig: Inclined Plane

 

 

Screw

A screw is an inclined plane wrapped around a nail. It consists of circular edges called thread. The pitch is the distance between two screw thread. The effort is applied to the head of the screw. It looks similar to nail and requires less effort to insert into the wood. Screw, nail, jack screw, etc.are some of the examples of the screw.Jack screw is used to lift the vehicles up to the certain height.

 

Source: www.gestiondecompras.com Fig:Screw

 

Wedge

Source: www.gestiondecompras.com Fig: Wedge

 

A wedge is a triangular shaped tool. Wedge consists of two or more sloping surfaces with one end sharp or pointed edge while the other one is a blunt edge. Here, the effort is applied at the blunt side. It is mainly used for cutting and splitting things, drilling holes etc. Some of the examples of wedges are axe, knife, nail, sickle, etc.

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