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Making Work Easier | Class 8 Science

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Last Updated: 01-03-2023

Simple Machines

Everyday, we use simple machines to helps us carry out daily tasks. Can you name any simple machines you know? Here are examples:
Picture of a Hammer
A hammer is used to help drive nails into objects as well as remove them.
Picture of a Panga
- A panga is used to cut objects such as trees.
- Others can be a pair of pliers, jembe, saw, wheelbarrow and more.

Tools should be properly maintained to:
  • make them last longer
  • prevent them from rusting
  • avoid accidents
  • enable them to work efficiently.
Some of the ways that tools can be maintained is by:
  • repairing them when needed
  • sharpening the cutting tools regularly
  • cleaning them after use
  • oiling them to prevent rust when storing them
  • storing them properly

Balancing Weights

When balancing (such as on a see-saw), the heavy load should move closer to the turning point or the lighter object should move farther away from the turning point. Look at the image below
Picture of balanced weights

Movement, Motion and Force

- Movement is the change in position of an object caused by force.
- Force is defined as a push or a pull exerted on an object.
- Force is measured in newtons (N). It is named after Sir Isaac Newton.
- Force can:
  1. start a stationary object
  2. speed up a moving object
  3. change direction of an object
  4. slow down a moving object
  5. stop a moving object
Please note: An object can be stopped or changed direction only if the force applied is more than the opposite force.

Types of Forces

Gravitational Force (Gravity)

- It is a force that pulls objects towards the center of the earth such as a falling apple. It can also be defined as a force that pulls objects towards one another such as the sun and the earth.

Magnetic Force

- It exists in magnets.
- A magnet has both North (N) and South (S) poles
- Attracts magnetic materials such as iron (e.g iron nails, pangas and more).
- In magnetism, like poles repel while unlike poles attract. Consider the figure below:
Picture of like and unlike magnetic poles

Friction Force

- Friction is the force that opposes motion
- It acts on the opposite direction of a moving object.
Picture of Friction force on a moving object

Advantages of Friction
- Enables us to Walk
- Enables vehicles to move
- Helps when lighting a match stick
- Makes writing easier

Disadvantages of Friction
- Brings about ware and tear
- Makes work harder
- Produces unwanted heat

Ways to increase friction
- Friction can be increased by making the surface more rough e.g adding murram on road, adding treads on wheels, tires and shoes

Ways of reducing friction
  • using a lubricant
  • using rollers
  • streamlining objects
  • using ball bearings
  • smoothing out surfaces
Picture of a moving object on rollers


- A lever is a simple machine used to life heavy objects.
- Any lever has three parts: load, effort and fulcrum/pivot/turning point
- All levers are classified as either: First class, second class or third class levers. This is determined by the arranged of the Load(L), Effort(E) and Fulcrum(F).

First Class Levers

- Fulcrum is between the load and the effort e.g claw, hammer, pliers, see-saw
Picture of a First Class Lever

Second Class Levers

- Load is between the fulcrum and the effort e.g wheelbarrow, nut cracker.
Picture of a Second Class Lever

Third Class Levers

- Effort is between the fulcrum and the effort e.g Fishing rod, human hand, spade.
Picture of a Third Class Lever

Inclined Planes

- An inclined plane is a slope
- It makes work easier by increasing the effort distance - The greater the effort distance, the lesser the effort.
- Examples of inclined planes are: Ladders, Staircase, Wedge, Screw, road winding up a hill, Ramp
Picture of a Staircase
- The picture above shows a staircase. This is an example of an inclined plane.
- The picture below shows another example of an inclined plane - a road winding up a hill.
Picture of a road winding up a hill
The road above is found in South Central China, in the Zhangjiajie National Forest Park

Single Fixed Pulley

- A pulley is characterized by a wheel with a rope.
Picture of a Single Fixed Pulley

- A pulley makes work easier by changing the direction of the force.The effort is applied towards gravity which is much easier.
- A flag is an example of a single fixed pulley.

Characteristics of a Pulley

  • Effort is applied towards gravity
  • Effort applied is equal to the load
  • Effort distance is equal to the load distance
  • The pulley has no mechanical advantage

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