Work and energy

Deepesh kumar

9th – f

13Science

G.L.T SARASWATI BAL MANDIR

MOTION१. सं�यो�ग – विभा�ग – ग�ना� कर्म� संर्म�नार्म� |

(�शे वि�कदशे�नार्म� – १.१.२०)२. ग�रुत् – प्रयोत्ना – सं�यो�ग�ना�र्म� उत्क्षे पणर्म� |

(�शे वि�कदशे�नार्म� – १.१.२१)३.र्मणिणगर्मना� सं#च्योणिभासंप�णर्म� अदृष्टकरणर्म� |

(�शे वि�कदशे�नार्म� – ५.१.२५)

यह सं�स्कृ� त में� वै शे�षि�कृदशे�नमें� में� दिदय� जा� चु�कृ� ह |

Motion is the cause of conjunction ,disjunction and velocity .

Motion against gravity is due to effort and conjunction is the effort .

Motion of precious stones and compass needle is due to invisible cause .

OUR SEERS OBSERVED VARIOUS PHYSICAL LAWS

Sanskrit scientist : Yajnavalkya,Aryabhata,Brahmagupta

 .

Indian scientist : Kanada , Galileo.

International   scientist :

Sir Isaac Newton , Albert Einstein , Henry Cavendish .

FORCE AND

MOTION

•A force is simply a push or a pull.

•All forces have both size and direction.

NET FORCES

When two or more forces

are combined!

SOME TIPS:o Forces in the same

direction- add the two forces together.

+ =o Forces in different

directions- subtract the two and figure out which direction was the stronger of the two.

- =

BALANCED VS. UNBALANCED FORCES

• Unbalanced: when the net force on an object is not zero. These produce a change in motion.

• Balanced: when the net force on an object equals zero. These do not produce change in motion.

MOTIONWhen an object changes position over time when compared with a reference point we say that the object is in motion.

SPEED• The rate at which an object moves.

• Depends on distance traveled and the time it takes to travel that distance.

Velocity•The speed of an object in a particular direction.

•Velocity must always include a direction .

ACCELERATION

•The rate at which velocity changes.

•To change velocity (change speed or direction or both)

NEWTON’S LAWS OF MOTION

1

2

3

Newton’s First Law

(law of inertia)

An object at rest tends to stay at rest and an object in motion

tends to stay in motion unless acted upon by an unbalanced

force.

1

BALANCED FORCE

Equal forces in opposite directions produce no motion.

UNBALANCED FORCES

Unequal opposing forces produce an unbalanced force

causing motion .

Newton’s Second Law

Force equals mass times acceleration.

2

Newton’s Second Law

Force = Mass x Acceleration• Force is measured in Newtons

• Accleration of gavity Earth= 9.8 m/s2

• Weight is a measure of the force of gravity on the mass of an object

• Weight (force) = mass x gravity (Earth)

Newton’s Third Law

For every action there is an equal and

opposite reaction.

3

Newton’s 3rd Law• For every action there is an

equal and opposite reaction.

BOOK TOEARTH

TABLE TOBOOK

Action: rocket pushes on gases

Reaction: gases push on rocket

EXAMPLE

Work &ENERGY

WORK

WORK DONE ON AN OBJECT IS DEFINED AS THE MAGNITUDE OF THE FORCE MULTIPLED BY THE DISTANCE MOVED BY THE OBJECT IN THE DIRECTION OF

THE APPLIED FORCE . THE UNIT OF WORK IS JOULE : 1JOULE = 1 NEWTON X 1

METRE

FORCE

DISTANCE

Work = force x distance

W = F d

WORK = F (N) X D (M)

= NEWTON-METER OR JOULE(J)

Calculating Work

W = 0, if F = 0

W = F d

W = 0, if d = 0

No work done if object doesn’t move.

No work done, whenever there is no force.

UnitJoule (J) is a Nm

ENERGY The energy

possessed by an object is thus

measured in terms of its capacity of

doing work .

POTENTIAL AND KINETIC ENERGY

KINETIC

ENERGY

KINETIC ENERGY

Energy in MotionCALCULATING KE

KE = ½ m v2

POTENTIAL ENERGY

POTENTIAL ENERGYPotential energy is stored

energy P.E. = mass x gravity x height . P.E. = mgh