Solution
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.
An inclined plane : A wedge, A needle, A staircase, A slide, An axe, A knife
A pulley : The wheel of a flagpole, A crane
A lever : Nutcrackers, Scissors, An opener
Question 2:
Fill in the blanks using the proper word and complete the statements.
(a) The ....... in the centre, the .......... on one side and the ...... on the other side make a lever of the first order.
(b) The ..... in the centre, the ........ on one side and the ......... on the other side make a lever of the second order.
(c) The .......... in the centre, the ....... on one side and the........on the other side make a lever of the third order.
(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.
(b) To lift bricks to the top of a tall building.
(c) To cut vegetables.
(d) To draw water from a well.
(e) To hold a papad for roasting it.
Work
Machine
Type of machine
To remove the lid of a tin
Can opener
Inclined plane (Screw)
To lift bricks to the top of a tall building
Wheel and rope or crane
Pulley
To cut vegetables
Knife
Wedge
To draw water from a well
Water wheel and rope
Pulley
To hold a papad for roasting it
A pair of tong
Lever
Question 4:
Write the answers to the following questions in your own words.
(a) What is meant by simple machines?
Devices which are used for day-to-day work to perform the work efficiently, in less time and with less effort are called machines. The machines that have only one or two parts and have simple and easy structure are called simple machines.
(b) Mention the advantages of using a machine.
The advantages of using a machine are:
(c) What is meant by complex machines?
A machine made up of two or more simple machines is called a complex machine. It consists of different parts that carry out different task and together contribute to the working of the machine. The most common example is that of a bicycle.
(d) What is a lever ? How are the orders of the lever determined?
(A) Lever is a simple machine having three components, viz. fulcrum, load and effort. (1) The support at which the rod of a lever rests is called a fulcrum. (2) The rotation of a lever takes place around a fulcrum. (3) The weight lifted by a lever is called a load. The load arm is the arm from the fulcrum to the load. (B) The orders of the lever are determined depending on the position of the effort, the fulcrum and the load. Lever of second order: When the fulcrum and effort are situated at the two opposite ends of the lever and a load is placed in between them, we call it a lever of second order. For example, a nutcracker, a wheel-barrow, etc. Lever of third order: When the fulcrum and load is situated at the opposite ends of the lever and an effort is applied somewhere between them, we call it a lever of third order. For example, a pair of tongs, a fishing rod, etc.
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.
Wheel is a simple machine. If the heavy bag is to be lifted, it will require more effort. Instead, drawing it on wheels become easier and efficient. It consumes lesser time and lesser energy to carry a bag. Therefore, traveler’s bags have wheels.
(b) Machines have to be maintained.
(c) A bicyle is said to be a complex machine.
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 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.
| 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 |
In the above paragraph there are simple machines. Their fulcrum, load and effort are as follows. The type of lever used is dependent on these positions.
Simple machine
Fulcrum
Effort
Load
Type
see-saw
Centre
On one side
On the other side
First
Scissors
Centre
On one side
On the other side
First
Wheelbarrow
On one side
On the other side
Centre
Second
Lemon squeezer
On one side
On the other side
Centre
Second
Tongs
On the other side
Centre
On one side
Third