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LUIT Valley Academy : Jorhat, Class XI Project

Introducing “The FORWARDERS”

MEMBERS:

DEBOJANEE DUTTA

DIPSIKHA SAIKIA

PRATIKSHA SHARMA

PRIYADARSHNI BORDOLOI

ANUSHUYA GOGOI

SANGHAMITRA GOGOIUnder the Guidance of

Dr. Sanjan Hazarika (Prof. in Charge)

Work done

Work done by a force is equal to the product of

force and displacementW = F . x

Relation:The work done by a force is measured by a

dot product of force and displacement.If a force F acting on a body displaces it through a displacement d, then the work done by the force is given by W = F.d

If the force is not along the direction of displacement, the component of force along the direction of displacement should be considered

Fsinθ F

Fcosθ

d

Work done (W)=Fcosθ.d

UNITS OF WORK The S.I. unit of work is joule

1J = 1N × 1m = 1Nm

The CGS unit of work is erg.

1erg = 1 dyne× 1cm = 1dyne cm

1J = 10⁷ erg

TYPES OF WORK: Positive work:

Work done(W)=F.Scosθ=positive value[0≤θ≤90⁰]

Negative work:

Work done(W) = F.Scosθ = negative value [90⁰≤θ≤180⁰]

ENERGY:The ability to do work

Work done = Energy Spent

21

22

2

1

2

1 doneWork mvmv

ENERGY

KINETIC ENERGY POTENTAL ENERGY

½mv² mgh

Energy can neither be created nor bedestroyed

It is transferred from one object to another or from one form to another form

Law of conservation of energy

Momentum P = mv It is the amount of motion contained in a body

P a m

a v

KE = ½ mv2 mm

vm

2

P

2

222

2mE P

CONSERVATION OF

MECHANICAL ENERGY

This principle states that if only the conservative forces are doing work on a body , then its mechanical energy (KE+PE) remains constant.

As the force is conservative , then change in potential energy is given by-

ΔU= -F(x)Δx = negative of the work done

CONSERVATIVE FORCE NON-CONSERVATIVE FORCE

If the work done by the force is displacing an object depends onlt on the initial and final positions followed between the initial and final positions,such a force is known as conservative force

E.g: gravitational force

If work done by aforce in displacing an object from one position to anotherdependsupon the path between the two positions, such a force is called non-conservative force.

E.g:force of friction,tension

CONVERSION: ELECTRIC

GENERATOR CONVERTS MECHANICAL ENERGY INTO ELECTRICAL ENERGY ENERGY

Electric Motor

ELECTRIC MOTOR CONVERTS ELECTRICAL ENERGY INTO MECHANICAL ENERGY

Rotational and translational KEKE of translation = ½ mv2

KE of rotatation = 1/2Iw2

Total Energy = ½ mv2 +1/2Iw2

= ½ mv2 +1/2(2/5mR2)v2/R2

= ½ mv2 + 1/5 mv2

= 7/10 mv2

vv

vm

Imv

2

22

2

1 mgH (2)diver For

2

1

2

1 mgH (1)diver For w

Photo electric cells convert solar energy into electrical energy

PROBLEMS:1. A body of mass 5 kg initially at rest is subjected to a force of

20N. What is the kinetic energy acquired by the body at the end of 10 seconds?

2. If the kinetic energy of a body increases by 300%, by what % will the linear momentum increases?

Sol 1. a = F/m = 20/5 = 4m/s2

u = 0

v = u +at = 0 + 4 . 10 = 40 m/s

KE = ½ mv2 = ½.5.40.40 = 4000J

Sol 2.

..100..100P

P increasePercent

P P - 2P P -P P

momentumin Increase

2P

2mE2 2m(4E)

4E E100

300 E E E2m P

2mE P

cpcpx

POWER: Power of a person or machine is defined as the rate at which work is done or energy is transferred. If a person does work W in time t, then its average

power is given by-

Average power(Pav) = rate of doing work

=work done/time taken

=W/t

PROBLEMS: A man weighing 60 kg climbs up a staircase carrying

a load of 20 kg on his head. The staircase has 20 steps each of height 0.2 m. If he takes 10 seconds to climb, find his power.

The human heart discharges 75 ml of blood at each beat against a pressure of 0.1 m of Hg. Calculate the power of heart assuming that pulse frequency is 80 beats per minute. Density of Hg = 13.6×10³ kgm¯³.

THANK YOU ALL

LVA : JORHAT ASSAM