Скачать или смотреть Chapter 4 Energy- Simple Machine class 6 ICSE physics

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What are Machines- Functions of simple machine,
Terms Related to simple Machine,
Types of Simple Machine,
Lever,
Incline Plane,
Wedge,
Pulley,
Screw,
Wheel & Axle,
Care of Machine,
What are Machines?
Machine is a device which makes our work easier and faster.
Machines which are manually handled to perform some mechanical work are called simple machines.
For example hammer, screwdriver, knife, bottle opener, etc
What are Complex Machines?
Machines in which two or more simple machines work together are known as Complex machines for example wall clock, a stopwatch, bicycle, washing machine, etc
Functions of a simple machine
1. A machine multiplies force: A heavy can load can be raised using a machine by applying even less force a person can lift a car using a screw jack.
2. A machine help to change the direction of the force:
A person can easily draw a bucket full of water from a well with the help of a rope moving over a Pulley he applies force in the downward direction but the bucket move in the upward direction.
3. A machine can change the speed:
In a bicycle the speed of moving wheels is different from the speed with which you can rotate the pedals.
4. A machine makes the force to act at some desired point: While cutting paper or cloth using a pair of scissors you can observe that the point of action of force applied by you has changed.
5 . A machine enables us to do dangerous and unsafe work: Using a fire tongs we can lift a piece of burning coal from fire
Effort: It is the force apply to the machine
Load: It is the force exerted by the machine on an object on which the work is to be done.
Fulcrum: It is a fixed point about which the machine can turn while doing work. mechanical advantage it is measured by the ratio of the load to the effort.
Mechanical advantage: It is measured by the ratio of the load to the effort.
S.I unit – Load is Newton (N)
S.I unit – Effort is Newton (N)
S.I unit – M.A is No unit
4. Input: it is the work done on a machine, i.e., energy supplied to the machine.

5. Output: It is the useful work at done by the machine i.e., energy imparted by the machine


6. Efficiency of a machine : It is the ratio of the work done by the machine on the load to the work done on the machine by the effort is called efficiency of machine.
1. Lever
Lever is a rod which moves freely about a fixed point called fulcrum or pivot point.
The weight is to be moved is called load(L) or the resistance and the force applied on the lever is called effort(E).
The distance of the fulcrum from the point at which effort is applied is called effort arm of the lever.
The distance of the fulcrum from the point at which load acts is called its load arm.
According to the principle of a lever the turning effect of the effort at the fulcrum should be equal to the turning effect of the load at the fulcrum.
Effort × Effort arm = Load × Load arm
Mechanical advantage of a simple machine is the ratio of the load to the effort.
MA= Load/ effort
Hence for a lever we can also say that:
MA= Effort arm/ Load arm
First class Lever
when the fulcrum of a lever lies between the load and the effort is called first class lever. Generally effort arm is taken longer then the load arm.
First class Lever - example;
beam balance, see saw, pair of Scissors, etc.
Second class Lever
when the load on a lever lies between the fulcrum and effort is called a second class lever. In the second class Lever the load arm is always shorter than the effort arm. Thus, mechanical advantage of the second class Lever is always greater than one.
Second class Lever example
a door, a bottle opener
Third class lever:
When the effort applied on a lever lies between the fulcrum and the load it is called a third class lever. In a third class Lever the effort arm is always smaller than the load arm therefore, the mechanical advantage of the third class Lever is always less than 1 but these levers increase the speed.
Third class lever: example sugar tongs, fire tongs, fishing rods, etc.
The load arm of a lever is 10 cm and its effort arm is 40 cm long. What is the mechanical advantage of the lever?
The load arm of an ideal lever of first class is 20 cm long and its effort arm is 1 m long. How much load can be lifted by using an effort of 40 Newton?
An inclined plane is a sloping surface which helps us to make our work easier. Using an inclined plane we can easily raise even a heavy load up to a certain height . Thus, inclined plane acts as a simple machine and help us to multiply force.
An Inclined plane Is used at various places.
Ramp is provided at the main gate of a house to push up scooters motorcycles and bicycles into the house.
Ramps provided in the hospital so that we will chairs and stretchers of patients can be easily pushed.
The playground slide is yet another example of inclined plane.
A wedge is a simple machine that has two or more inclined surfaces which taper each other to form a sharp