Force , work and Energy

Force  , work and energy

 To move anything , we  either pull it or push it  when e  play cricket ,  , We push the  ball with the bat . During cycling  we push the pedals  of the  cycles  to move  it . To open a door , we  either  push it .

A push or pull on an object is called force

Some  other  examples  of push or pull are shone in the picture  given along side

A force does not move  an object  always  for examples , if we  apply force  on a wall, it does not move .

 Effect of force

 Force can affect an object in many ways . Let us learn about these effects

 1.Force can stop a moving object  in opposite direction, the objects  shows or stops   for examples  force   applied  by a player  on moving  football, stop it

2. Force can move a stationary object

 When you apply force on a stationary objects , it moves  the objects  in the direction of  applied  force . For examples, a player moves  a football; by kicking  it .

 3.Force can change the direction of moving objects

 We apply force on the steering wheel to change the direction of moving  car

 4.Force can change the shape of the  an object

 When you presents  an inflated  balloon full of air , its  shape changes when you make  chapattis , the force  applied  by your  hand  changes the shape of the dough

 Types of force

Magnetic force

 When you bring  a magnet near iron nails , it attracts  the nails . The  force applied  by a magnet  on an objects  is called  magnetic  force

Electrostatic force :

 When you comb your dry hair and bring the comb near tiny bits  of paper , the paper gets attracted  towards  the comb. This  is  because  on  rubbing m, the  comb gets  charged  and attracted  tiny bits  of paper . so when things  are rubbed  with each other , they become  charged  and force of attraction is produced . this force of attraction  is called  electrostatic  force .

Gravity or Gravitational force

Every things that you through up in the air , comes  down, ripe  fruit s always  fall on the  earth’s  from a tree. You cannot jump beyond a certain height. Do you know why? Our earths exerts a force on every objects, that attracts  the object towards  its centre . This  force is called  gravity or Gravitational force

 

Force  of  friction :

 When we roll a ball on the floor , it  gradually  slows  down and finally stops . in the same  way , even you stop  paddling  you cycle, it gradually  slow does not  and stops. Why does ball or cycles stop[s?  they stop because  a force  acts between  the  ball or cycles  and  the floor  that slow down the ball or cycles . this force is called  frictional fore or  force of friction. A force  that slows down the movement of an objects  on a surface  is called  force of friction or frictional force .

Advantages of friction

 It helps us  to walk. We can not walk easily on a road  very smooth surface  or wet  floor  because there  is very less  friction and we  may slip on the floor

 Friction between road  and tyres of automobiles  makes  their movement possible

 You are able  to write  with your pen because  of friction. You often see that you cannot write  easily on oily paper . this  is because  there is very less friction  between our  pen and oily paper

Friction also helps to erase pencils marks from  the paper  by using  an eraser

Disadvantage of  friction :

 It slow down or stops the motion of an objects

Friction produce  heat that damage  the machine s . That is why we  use oil in sewing  machines cycles , etc

Friction damage the  tyres of  vehicles  and  soles  of our shoes

 Work Ram is reading  a book. Anuj is pulling  a toy car. Now  tells  who is doing  work? Anuj is doing  work Surprised ! in Science ,  work is said  to be done  only when  force  change s the position of an objects . Anuj is applying  force  to mover  the toy car . Car is changing  its position. So he is  doing  work. Thus  work is said  to be  done  only when the applied  force  change s the  position of the objects . for  Example s, when  you push a  table  and it moves , then work is done . when you push an almirah with all the force  you have , there is no change  in its position. Then, no work is done .

Energy :

The ability  to do work is called  energy . to perform any activity like  playing , reading , and sleeping , we need  need  energy ,even machines  need  energy  to work 

 

Types of energy :

1.Heat energy: Energy that we get from heat is called heat energy. This energy is produced by burning fuels, like coal LPG and Kerosene. we use  heat energy to cook food .

2. Light energy: Energy that we  get from  light  is called  light  energy . It is produced by bulb, CFL(Compact fluorescent  lamp) candles  etc. We  are able to  see  with the help[ of light  energy.

3.Kinetic Energy: The energy of  an objects  due to its movement is called  kinetic energy.  A moving  bus, moving  cycles, running  boy , etc , have  kinetic energy.

4.Potential energy:

The Energy stored  in an objects  due  to its  position is called  potential energy. The  water  stored  in a  tank on the roof  has potential energy because  it is stored  at a height .

5.Mechanical energy: The energy in an object due  to its  position (( potential energy ) and  its movement (( Kinetic energy ) is called  mechanical energy. The water stored behind a dam in the reservoir  has  potential energy that changes  into kinetic energy when the water fall down from a 

 certain height .

6.Electrical energy: The energy that we  get  from electric current  is called  electrical energy it ios used to ru  electrical appliance  like  television and washing  machine . it is  generated  at power station and supplied  to our homes 

7.Wind energy : The energy  that we  get  from the wind (morning air ) is called  wind energy . It is used  to generate  electricity by using  a windmills

8.Solar energy: The energy of the  sun is called  solar energy. It is used  to cook food in solar  cookers , to heat water  in solar heater , etc . It is also used  in solar calculator  and  solar watches

9.Hydro energy: The energy of the flowing  water  generates  electricity in hydroelectric power  plants . The  electric  energy so generated is called  hydroelectricity