Subject: Science
We use various types of machine in our daily life to perform various activities. These machines make our work easy and efficient. For example, we use a knife to chop vegetables, scissors to cut papers, beam balance to measure weight, bottle opener to open the bottle, etc. There are a simple machine and complex machine. Forceps, punching machine, crowbar, bottle opener, etc. are examples of the simple machine while motorcycle, truck, car, etc. are some examples of the complex machine. A simple machine is a device, which is simple in structure and makes our daily work easier, faster and more convenient.
Mainly, there are six types of simple machines, which are given below,
Lever is a type of simple machine that is used to lift the heavy loads. It is made of a rigid bar that moves about a fixed point called fulcrum. It consists of three parts, effort arm, fulcrum and load arm. Fulcrum is the point where rigid bar rotates. By applying effort in effort arm the load is lifted by the help of fulcrum. Effort arm is the distance between the fulcrum and the point where effort is applied and load arm is the distance between fulcrum and load where the load is kept. Input work is equal to output work in an ideal lever which is the balanced condition of the lever. It is the principle of the lever.
Levers are of three types depending upon the positions of fulcrum, load, and effort which are as follows,
Activity 1
Bring a rigid bar, one heavy stone, and two bricks. Then, lift the stone without using a rigid bar. Place stone in the one end of the bar and place the middle part of the bar in the bricks of a certain height. Then, apply the effort on the other end of the bar. What do you conclude from this experiment? What is the reason behind it?
A pulley is a simple machine consisting grooved circular disc and a rope. The rope passes over the circular disc. In pulley, a load is attached to one end of the rope while the effort is applied at the another end of the same rope. Here, the effort is applied in a convenient way which makes our work easier. There are two types of the pulley on the basis of their movements. They are as follows,
Activity 2
Lift the water from the well by using a pulley. The water bucket moves upward though you are pulling the rope downward. What do you conclude from this experiment? What is the reason behind this?
It consists of two cylinders having a different radius. Cylinder with a small radius is axle and cylinder with a large radius is a wheel. Formally, a rope is coiled in wheel and axle. The effort is applied in wheel and load in the axle. They move in the same manner but the distance covered is different due to the difference in radius. Since effort applied on the wheel is magnified so, by applying small effort on the wheel, heavy loads can be lifted. Some of the examples of wheel and axle are paddle of the bicycle, a drill used by carpenters, steering of vehicles, etc.
Activity 3
Ride and use the paddle of the bicycle. You can find that the tyres move faster though you paddle slowly. What do you conclude from this experiment? What is the reason behind this ?
It is very difficult to load heavy things onto a truck or some area of a certain height. A huge effort is needed. In such case, the inclined plane is used. It is a sloping surface or a wooden plank. It multiplies the applied effort. It helps to push the heavy load upward easily. The winding road, staircase, ladder, etc. are the examples of an inclined plane.
Activity 4
Bring a sloping surface or a wooden plank and a heavy load like a small drum. Then lift the drum up to the certain height without using the wooden plank. After this, again lift the drum in the same height by using wooden plank i.e. inclined plane. What do you conclude from this two activity? What is the reason behind it?
A screw is an inclined plane wrapped around a nail. It consists of circular edges called thread. The pitch is the distance between two screw thread. The effort is applied to the head of the screw. It looks similar to nail and requires less effort to insert into the wood. Screw, nail, jack screw, etc.are some of the examples of the screw.Jack screw is used to lift the vehicles up to the certain height.
Activity 5
Bring a screw and the wood. Then insert the screw in the wood by rotating its head instead of pressing it inside. The screw moves downward though we don’t press the screw. What is the reason behind it?
A wedge is a triangular shaped tool. Wedge consists of two or more sloping surfaces with one end sharp or pointed edge while the other one is a blunt edge. Here, the effort is applied at the blunt side. It is mainly used for cutting and splitting things, drilling holes etc. Some of the examples of wedges are axe, knife, nail, sickle, etc.
Activity 6
Bring a knife and a small piece of wood. Then cut the piece of wood with the help of the knife. Though you hit the piece of wood in the straight direction or apply force in one direction (vertical), the woods gets separated (horizontal force). What is the reason behind it?
Activity 7
Identify the simple machines given below. Classify them and write down their uses and types. What do you learn from this activity? Write down your conclusion.
S.N. | Names of simple machine | Types of Simple machine | Uses |
The importances of simple machine is as follows:
Name any five types of simple machine and give two examples of each.
Any five types of simple machine with two example of each are given below,
What is lever? Name its types with two examples of each.
A lever is a rigid bar which moves freely about a fixed point called the fulcrum. There are three types of lever which are as follows,
What do you mean by input and output work? Write down the principle of the lever.
The work done on a machine is called the input work and the useful work done by the machine is called the output work. The principle of lever is given below,
In ideal lever when it is in balanced condition then,
Input work = output work
Or, Effort \(\times\) effort arm = Load \(\times) load arm.
Define wedge. Write down any three examples of wedge.
A wedge is a simple machine having two or more sloping surfaces that taper either to form a sharp edge or pointed edge. Any three examples of wedge are axe, knife, and needle.
Write down any three advantages of using simple machine in our daily life.
Any three advantages of using simple machines in our daily life are as follows,
What is pulley? Write down types of pulley.
A pulley is a simple machine having a grooved circular disc over which a rope passes. There are three types of pulley which are as follows,
A bottle opener is a second class lever. Why?
A second class lever is a type of lever in which load is situated between the fulcrum and the effort. Since in bottle opener, the load ( bottle cork) is situated between the fulcrum and effort so the bottle opener is a second class lever.
Classify the given simple machines.
Simple machines: Beam- balance, nut- cracker, flag pole, screw- driver, ladder, nail and axe.
The simple machines with their types are given below,
Write down any five simple machine used in your homes and write down their uses.
Any five simple machines used in our homes are as follows,
Why is shovel not called second class lever?
In second class lever, load is situated between the fulcrum and the effort and in third class lever the effort is situated between the fulcrum and the load. Since in shovel, the effort is situated between the fulcrum and load so it is called third class lever but not a second class lever.
What are the differences between simple machines and complex machines?
The differences between simple machines and complex machines are as follows,
Simple machines |
Complex machines |
They are simple in structure. |
They are complex in structure. |
Their mechanism is very simple and is very easy to understand and operate. |
Their mechanism is very complex which is difficult to understand and operate. |
Examples: scissors and beam balance |
Examples: car and truck |
What are the differences between first class lever and third class lever?
The differences between first class lever and third class lever are as follows,
First class lever |
Third class lever |
In the first class lever, the fulcrum is situated between the effort and the load. |
In the third class lever, the effort is situated between the fulcrum and the load. |
Effort arm of a first class lever is longer than the load arm. |
Effort arm of a third class lever is shorter than the load arm. |
Example: beam balance and see- saw. |
Example: fishing rod and shovel. |
What are the differences between input work and output work?
The differences between input work and output work are as follows,
Input work |
Output work |
The work done on a machine is called input work. |
The useful work done by a machine is called output work. |
It is done by the persons. |
It is done by the machine. |
Example: flour, salt, and eggs are put in a machine by men to makes noodles. |
Example: Noodles are made by machine using flour, salt, and eggs |
What are the differences between fixed pulley and movable pulley?
The differences between fixed pulley and movable pulley are as follows,
Fixed pulley |
Movable pulley |
Fixed pulley is a type of pulley in which pulley does not move with the load. |
Movable pulley is a type of pulley in which pulley moves along with the load. |
It does not multiply the force. |
It multiplies the force. |
Examples: pulley used to lift the water from the well. |
Examples: pulley used in construction crane and modern elevators. |
A load of 100N can be lifted by applying an effort of 25N. If the load arm is 25cm, calculate the effort arm.
Solution:
We have,
Load = 100N
Load arm = ?
Effort = 25N
Effort arm = 25cm
Now, by using principle of lever
Input work = Output work
Or, Effort \(\times\) effort arm = Load \(\times\) load arm
Or, 25 \(\times\) effort arm = 100 \(\times\) 25
Or, Effort arm = \(\frac{100 \ times 25}{25}\)
Or, Effort arm = 100cm
\(\therefore\), The load arm is 100cm.
An effort of 25N is applied to lift the load. If the load arm and effort arm is 20cm and 25cm respectively, then calculate the load.
Solution:
We have,
Effort = 25N
Effort arm = 20cm
Load arm = 25cm
Load = ?
Now, by using principle of lever
Input work = Output work
Or, Effort \(\times\) effort arm = Load \(\times\) load arm
Or, 25 \(\times\) 20 = load \(\times\) 25
Or, Load = \(\frac{25 \ times 20}{25}\)
Or, Load = 25N
\(\therefore\), The load is 25N.
An effort of 50N is applied to lift the load of 75N. If the load arm is 100cm then find the effort arm.
Solution:
We have,
Load = 75N
Load arm = 100cm
Effort arm = ?
Effort = 50N
Now, by using principle of lever
Input work = Output work
Or, Effort \(\times\) effort arm = Load \(\times\) load arm
Or, 50 \(\times\) effort arm = 75 \(\times\) 100
Or, effort arm = \(\frac{ 75 \times 100}{50}\)
Or, effort arm = 150cm
\(\therefore\), The effort arm is 150cm.
To lift the load of 100N, an effort is applied. If the load arm is 50cm and the effort arm is 20cm then what is the effort applied?
Solution:
We have,
Load = 100N
Load arm = 50cm
Effort arm = 20cm
Effort = ?
Now, by using principle of lever
Input work = Output work
Or, Effort \(\times\) effort arm = Load \(\times\) load arm
Or, Effort \(\times\) 20 = 100 \(\times\) 50
Or, Effort = \(\frac{ 100 \times 50}{20}\)
Or, Effort = 250N
\(\therefore\), The effort applied is 250N
Calculate the input work and output work if effort applied is 10N and effort arm is 20cm, and load is 25N and load arm is 5cm.
Solutions:
We have,
Load = 25N
Load arm =10cm
Effort arm = 20cm
Effort = 10N
Now, by using principle of lever
Input work = Effort \(\times\) effort arm
= 10 \(\times\) 20
= 200.
Output work = Load \(\times\) load arm
= 25 \(\times\) 5
= 50.
\(\therefore\), The input work is 200 and output work is 50.
An effort of 5N is applied to lift the load of 50N. If the effort arm is 10m, calculate load arm, input work and output work.
Solution:
We have,
Load = 50N
Load arm = ?
Effort arm = 10cm
Effort = 5N
Now, by using principle of lever
Input work = Output work
Or, Effort \(\times\) effort arm = Load \(\times\) load arm
Or, 5 \(\times\) 10 = 50 \(\times\) load arm
Or, load arm = \(\frac{ 5 \times 10}{50}\)
Or, load arm = 1m
\(\therefore\), The load arm is 1m.
Now,
Input work = effort arm \(\times\) effort
= 10 \(\times\) 5
= 50.
Output work = load arm \(\times\) load
= 2 \(\times\) 50
= 100.
\(\therefore\), The input work is 100 and output work is also 100.
An effort of 5N is applied to lift the load of 50N. If the effort arm is 10m, calculate load arm, input work and output work.
Solution:
We have,
Load = 50N
Load arm = ?
Effort arm = 10cm
Effort = 5N
Now, by using principle of lever
Input work = Output work
Or, Effort \(\times\) effort arm = Load \(\times\) load arm
Or, 5 \(\times\) 10 = 50 \(\times\) load arm
Or, load arm = \(\frac{ 5 \times 10}{50}\)
Or, load arm = 1m
\(\therefore\), The load arm is 1m.
Now,
Input work = effort arm \(\times\) effort
= 10 \(\times\) 5
= 50.
Output work = load arm \(\times\) load
= 2 \(\times\) 50
= 100.
\(\therefore\), The input work is 100 and output work is also 100.
Define lever.
A lever is defined as a rigid bar that moves freely about a fixed point called the fulcrum.
Give any two examples of wedge.
Any two examples of wedge are axe and knife.
What is third class lever?
The lever in which the effort is situated between the fulcrum and the load is called the third class lever.
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