Simple Machines - Standard 6 - General Science - Balbharati

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 12. Simple Machines 

Exercise

Q. 1 Classify the following as a lever, a pulley and an inclined plane.

Ans.

Lever: Nutcrackers, scissors, opener.

Pulley: Crane, wheel of a flagpole.

Inclined plane: Staircase, slide.

Others (Wedge type): A wedge, a needle, an axe, a knife.


Q. 2 Fill in the blanks using the proper words and complete the statements.

(a) The fulcrum in the centre, the load on one side and the effort on the other side make a lever of the first order.

(b) The load in the centre, the fulcrum on one side and the effort on the other side make a lever of the second order.

(c) The effort in the centre, the fulcrum on one side and the load on the other side make a lever of the third order.


Q. 3 Which machines will you use to do the following work? Write their types.

(a) To remove the lid of a tin.

Ans. Opener — Lever of the first order.

(b) To lift bricks to the top of a tall building.

Ans. Pulley — Simple machine.

(c) To cut vegetables.

Ans. Knife — Wedge type of simple machine.

(d) To draw water from a well.

Ans. Pulley — Simple machine.

(e) To hold a papad for roasting it.

Ans. Tongs — Lever of the third order.


Q. 4 Write the answers to the following questions in your own words.

(a) What is meant by simple machines?

Ans. The devices which help us to do work easily with less effort are called simple machines. They have few parts and a simple structure. Example: Lever, pulley, inclined plane.

(b) Mention the advantages of using a machine.

Ans. Machines make our work easier, save time, reduce effort, and help us perform heavy or difficult tasks conveniently.

(c) What is meant by complex machines?

Ans. Machines made up of two or more simple machines joined together are called complex machines. Example: Bicycle, sewing machine, crane.

(d) What is a lever? How are the orders of the lever determined?

Ans. A lever is a simple machine consisting of a rigid rod that rotates about a fixed point called the fulcrum. The position of the fulcrum, load, and effort determines the order of the lever.


Q. 5 Give reasons.

(a) Traveller’s bags have wheels.

Ans. Traveller’s bags have wheels so that heavy loads can be moved easily with less effort using the principle of a wheel and axle.

(b) Machines have to be maintained.

Ans. Machines have to be maintained because friction, dust, and rust can damage their parts. Regular cleaning, oiling, and covering reduce wear and tear and increase their lifespan.

(c) A bicycle is said to be a complex machine.

Ans. A bicycle is a complex machine because it is made up of several simple machines such as levers, pulleys, and wheel and axle systems working together.


Q. 6 Name the levers mentioned in the following passage. Identify the fulcrum, load and effort of each and say which type of lever it is.

Machine Fulcrum Load Effort Type of Lever
Sea-saw Centre support Child on one end Child on the other end First order
Wheelbarrow Wheel Load in the tray Hands lifting handles Second order
Lemon squeezer Joint of the squeezer Lemon between plates Hand pressing handles Second order
Tongs Joint at one end Object held between tips Hand in the middle Third order

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