Manash (Subhaditya Edusoft): Centrifugal Force , Motion and Levers for Balance, Movements and Work

Centrifugal force Page to my Physics-World Software

CENTRIFUGAL FORCE :

If you swing a bucket of water over your head fast enough the water will not come out. When anything is spun round in a circle there is a force acting in it directly outward from the center of the circle . This is called the centrifugal force.It happens because the object wants to continue to move in a straight line.

The force depends on the speed with which the object is going round.The greater the speed of rotation is .The greater the force.

You can feel centrifugal forces pushing you outwards when a car takes a bend quickly. and on round about in fair grounds.On roundabouts the force may be so strong.That you have to hold tightly to stay on the same effect .occurs on the wall of death. As you spin round you are pushed outwards against the wall.Because you spin rapidly the force is great enough to stop you falling.

when a bucket of water is swung round quite quickly. A centrifugal force pushes the water into the bucket.If, when the bucket is above your head, this force is greater than the weight of the water, the water will not fall out.

The Moon and the Artificial satellites orbit the earth

CENTRIPETAL FORCE:

There is another force equal but opposite in direction , to the centrifugal force. Called the centripetal force.This is the force acting towards the center of the circle, that keeps the bucket moving in circle. If the there is no centripetal force the bucket would fly off in a straight line.

Centrifugal and Centripetal are Two opposite forces

When you swing the bucket, you can feel a pull in your arm.This is what provides the centripetal force.The centrifugal force acts outwards from the center,While the centripetal force acts towards the center.

If you swing the bucket more slowly you will find out what happens to these forces.The slower the swing the smaller the force. So now there is less centrifugal force pushing the water into the bucket.If this force is less than the weight of water, then the water is begin to fall out.At the same time, the centripetal force, the pull in your arm,Gets less.

The centrifugal force balances the force of gravity in the solar system.The earth and the sun are both very large masses.So there is a large force of gravity between them.Since they do not crash into each other there must be another force pulling them apart.This is the centrifugal force caused by the earth travelling in its orbit round the sun.

These two forces oppose each other in the solar system. The force of gravity acts as centripetal force.Opposing this is the centrifugal force caused by the motion of the planets round the sun.The planets do not have air resistance to slow them down.So they keep moving round.

The gravitational attraction between the earth and the moon or the satellites is balanced by their centrifugal forces.

3D Animation Showing Gravitational and Centrifugal forces

In the same way the moon and the artificial satellites orbit the earth. The gravitational attraction between the earth and the moon or the satellites is balanced by their centrifugal forces.

Escape from the earth gravity , a rocket has to go into the orbit round the earth

Escape from the earth gravity , a rocket has to go into the orbit round the earth , it must accelerate until the centrifugal force due to its circular motion is greater than the force of gravity pulling it towards the earth . The speed which has to be reached is called the escape velocity .The force of the gravity on the moon is much lower, so the escape velocity from the moon is also lower.

Rotation Page from my Physics-World Software

ROTATION:

If you spin a coin on a table it will have two kinds of motion .Firstly it will move across the table ,and secondly it will spin round and round on its own axis. These two motions are quite separate. In the same way,when a golf ball is flying through the air it is both spinning and changing its position.

Different Types of Motion

Spinning objects have special properties . The most important of these is that they tend to resist any change in the direction of spin. You can feel this by doing a simple experiment with the front wheel of bicycle . Lift the wheel off the ground and spin it round .Now move the handle bar from side to side.You can feel a force that rises to stop you .This is the inertia of the wheel resisting a change in then direction of axis of the spin. In the case of the bicycle wheel the axis is the wheel axle. This inertia of spinning objects is called gyroscopic inertia.

A Gyroscope is a small heavy wheel

GYROSCOPES:

A gyroscope is a small heavy wheel mounted so that it can move about any axis .This is called a universal mounting. The wheel will always tend to keep spinning in the direction in space in which it started spinning.

The rapidly spinning inner wheel will maintain its direction in space if the outside framework Changes

The principle of the gyroscope is used in the gyro-compass. This device is used in ship and aircraft.The wheel is kept spinning electrically with a compass mounted over it. The spinning wheel of the gyroscope ,because of its inertia , is unaffected by the motion of the ship.It will therefore always point to true north.

Gyro pilot : This is an instrument for steering a ship automatically

The similar device is gyro pilot .This is an instrument for steering a ship automatically.It is let to course of the ship .Any change of the course is detected by the gyro pilot because it stays pointing its original direction . The gyro pilot sends a message to a motor controlling the rudder .The rudder then brings the ship back on the course again.

A Frisbee spin rapidly while it moving through air

The property of spinning objects is called spinning stabilization.A frisbee spin rapidly while it moving through air .If it did not spin,it would not stay horizontal and so would not travel far.

Circus performers spinning plates on the tips of the long stick

You may have seen circus performers spinning plates on the tips of the long stick. The plates remain horizontal because they are stabilized by their spin. The plates do not want to change direction of their axis of their spin . Once they started slowing down the spin stabilization gets much less and they soon fall off the stick. The skill of juggler is to keep its stick moving so that it keeps the plate spinning . A spinning top stay balanced for the same reason .It is stabilized by its spin.

The earth is also spinning round on its axis .This keep the axis pointing in one direction in space ,Just as the spinning of a gyroscope keeps it pointing in its original direction.

KINDS OF MOTION:

There are two types of motion 1) Translational motion 2) Rotational motion. Translational motion is again divided into two types A) Rectilinear motion B) Curvilinear motion

3D Animation Showing Different Types of Motions

There are two types of motion 1) Translational motion 2) Rotational motion. Translational motion is again divided into two types A) Rectilinear motion B) Curvilinear motion

If every particles of moving body move in a way that position of connecting straight line of any two particles in various time is become parallel to each other, then the motion of the moving body is called Translational motion . If the translational motion occur in straight line call A) Rectilinear motion. Ex:- Motion of train, Motion bullet from revolver.

When translational motion occur in curve line called B) Curvilinear motion. Ex:- Movement of the chair of the rotating giant wheel.

If a body rotate around in its own axis then its motion called Rotational motion. Ex:-motion of top, electric fan etc.

Lever Page from my Physics-World Software

LEVERS:

Place a 30 cm ruler on a table with a pencil under it . You will find that the ruler only balances when the pencil is under neath the 15 cm mark. Now place one coin on the 0 mark and another on the 30 cm mark. The ruler will still balance.You will also find that one coin on the 7.5 cm mark is balanced by one on the 22.5 cm mark. The ruler is balanced by equal weights or forces at equal distances from the center.

What happens if you try to balance one coin at the 0 mark with coins at the 22.5 cm mark? you will find that for it to balance you will find that for it to balance you will need two coins at this 22.5 cm point. If the distance from the center is halved.The weight or force must be doubled.

MOMENTS:

Moment of Inertia

These coins are trying to turn or rotate the ruler.This tendency of a weight or force to rotate an object is called a moment .From the ruler experiment you can see that the moment does not only depends on the distance that the force is from the point of balance (the 15 cm mark). The point of balance is called the fulcrum.

Seesaw Lever

The moment of a force is equal to the force multiplied by its distance from the fulcrum. When the ruler is balanced.The moments of the two forces must be equal in order to cancel each other out.In the last case we had one coin 15 cm from the center. This gives a moment of 1*15 = 15 units.The other side had two coins 7.5 cm from the center,giving a moment of 2 * 7.5 which also equals 15 units. that is why the ruler balanced .Try different weights and distances to see what happens.

Simple balance Picture

Moments are used in a simple balance, like an old pair of kitchen scales.Weights are put on a pan on one side to balance the food to be weighed on the other side.The distances from the center, or fulcrum, are the same .So when the correct weight is put in the pan .The moments on both sides of the balance are equal.The system is said to be equilibrium.

A lever is also uses moments.You can often prise a rock out of the ground by using a crow bar.You put a stone under the crowbar near the rock .The stone acts as fulcrum .Then you push down at the other end of the crowbar, which is a greater distance from the fulcrum than the rock .In this way,you produce a greater momentum than could by trying to roll the rock out of the ground.

The weight of the rock is called the load. The force with which you push down is called the effort . When the moment of your effort is greater is greater than the moment of the load.The rock moves.

Seesaw is a 1st Class Lever

There are 3 classes of levers.One is like the crowbar, In which the fulcrum is between the load and the effort .In the second class, The fulcrum is at one end , the effort at the other , and the load is between the two. An example of this is a wheelbarrow.In the 3rd class the fulcrum is at one end , the load at the other, and effort in between.Sugar tongs are an example of this class.