- In our day-to-day life, we use simple or complex machines depending upon the task to be carried out and the time and efforts required to do it.
- Machines are used for reducing efforts, and doing more work in less time.
- Some machines are simple while others are complex.
- The wedge, the lever, the inclined plane, the pulley and the wheel and axle are simple machines.
- There are three types of levers based on the positions of effort, load and fulcrum.
- Machines should be maintained properly to keep them in good working condition.
Question 1: classify the following as a lever, a pulley and an inclined plane :
A wedge, a needle, a staircase, a slide, the wheel of a flagpole, nutcrackers, scissors, an opener, an axe, a crane, a knife.
- A wedge: An inclined plane
- A needle: An inclined plane
- A staircase: An inclined plane
- A slide: An inclined plane
- The wheel of a flagpole: A pulley
- Nutcrackers: A lever
- Scissors: A lever
- An opener: A lever
- An axe: An inclined plane
- A crane: A pulley
- A knife: An inclined plane
Question 2 : Fill in the blanks using the proper word 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 load on one side and the fulcrum on the other side make a lever of the third order.
Question 3: Which machines will you use to do the following work? Write their types.
a) To remove the lid of a tin.
Answer : To remove the lid of a tin, we should use an opener which is a second order lever.
b) To lift bricks to the top of a tall building
Answer : To lift bricks to the top of a tall building, we should use a crane which is a pulley.
c) To cut vegetables
Answer : To cut vegetables, we should use a knife which is a wedge.
d) To draw water from a well
Answer : To draw water from a well, we should use a pulley system or wheel-axle.
e) To hold a papad for roasting it
Answer : To hold a papad for roasting it, we should use a tong which is a third order lever.
Question 4: Write the answers to the following questions in your own words.
a) What is meant by simple machines?
Answer : a) Simple machines are the tools that help people work faster and better. These help us lift heavy loads, change the speed of the motion or the direction of force. Examples are simple machines are knife, nutcrackers etc.
b) Mention the advantages of using a machine.
Answer : The advantages of using a machine are: More work can be done in lesser time as well as with great accuracy Less effort has to be applied to accomplish the task.
c) What is meant by complex machines?
Answer : A complex machine is a machine made up of two or more simple machines that make your work easier to do. There are six simple machines from which all complex machines are made. They include: The lever. The inclined plane.
d) What is a lever ? How are the orders of the lever determined?
Answer : The orders of the lever are determined depending on the position of the effort, the fulcrum and the load. Lever of first order: When the fulcrum is situated between load and effort, we call it a lever of first order. For example, beam balance, a crowbar, a see-saw.
Question 5: Why is this so?
a) Traveller’s bags have wheels.
Answer : Since luggage has to move here and there,so to reduce the friction luggage has wheels.It reduces the contact area making more easy to move. 2. Aeroplane has also a streamlined shape to reduce the friction produced by air.
b) Machines have to be maintained.
Answer : Employers have a legal obligation to ensure correct maintenance of machinery in the workplace. This helps to reduce any risks as a result of unexpected failures and helps to keep the work-force safe.
c) A bicyle is said to be a complex machine.
Answer : A bicycle is composed of many simple machines, such as a screw, wheel and axle, lever, pulley, which carry out different task and together contribute to its working. Thus, the bicycle is said to be a complex machine.
Question 5 : Name the levers mentioned in the following passage. Identify the fulcrum, load and effort of each and say which type of lever it is.
Ravi and Savita sit on a sea-saw in a garden. In the mean time, a gardener is trimming trees in the garden. He puts the leaves and other garbage in the wheelbarrow. Later, Ravi gets thirsty and he buys lemon sherbet. The sherbet seller cuts the lemon and squeezes it using a lemon squeezer. He puts small pieces of ice in the glass with the help of the tongs.
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