Making Work Easier - Class 7 Science Revision Notes

• Friction.
  • Advantages of Friction.
  • Disadvantages of Friction.
  • Ways of Reducing Friction
  • Ways of Increasing Friction.
• Levers
  • First Class Lever
  • Second Class Lever
  • Third Class Lever.

Friction.

This is a type of force that occurs between two objects that are in contact.

Advantages of Friction.

• It helps in walking.
• Makes it possible to produce fire using a match stick.
• Helps in writing in both boards and books.
• Helps in rubbing or erasing.
• Helps in braking of vehicles and bicycles.

Disadvantages of Friction.

• Causes wearing out of objects eg bicycle tyres,soles, shirts etc
• It makes work difficult eg its difficult to pull or puss an object on a rough surface.
• Production of unwanted heat.

Ways of Reducing Friction.

1. Using rollers.
2. Smoothing/Polishing surfaces.
3. Using lubricants
4. Streamlining.

Ways of Increasing Friction.

1. Spreading of some course materials on the slippery grounds e.g murram.
2. Using tyres with treads
3. Replacing worn out parts of tools
4. Replacing of shoe soles.
5. Applying of glue on the surfaces.

Levers

These are simple machines that makes work easier.

They have Load, Effort and Fulcrum.

Load:- This is the work to be done
Effort:- This is the part which is held in the tool.
Fulcrum:- This is the turning point of the tool or of the tool and the part which is held.

First Class Lever

Here the fulcrum is in between the load and the effort as in.

• Crowbar
• Claw hammer.
• A pair of scissor
• Pliers etc

Second Class Lever

Here the load is in betwee the fulcrum and effort

• Wheelbarrow
• Door hing
• Lid opener
• Bottle opener etc

Third Class Lever.

Here the effort is in between the load and the fulcrum

• Spade
• Spoon
• Fishing line etc