ALLAH IS THE BEST CREATOR OF NATURAL BEAUTY

What they are What they are Doing?Doing?

a. What is Work?b. What do you mean

by 1J work done.c.Calculate the work

done by the man against the gravity

d.Compare the man’s work done with another body of same mass when raised through an inclined plane making an angle of 300 with the horizontal plane (length of the stair =3m)

Mass of the man 80 Kg

Height

of e

ach

step

=10

cm=

0.10

m

No o

f ste

p= 2

0

WorkWorkWork is

defined as the product of force and

displacementTherefore

Work done W = F x S

DisplacementF

FORCES

Work is the success of the application force on an object which can produce displacement

Classification of workClassification of work

++VVe e WORK DONEWORK DONE

Work done W = F x S cos θ= F S cos θ

Displacement

F

FORCE Applied Below C.G

Accepted Displacement

S

S si

n θ

S cos θ

0 ≤ θ >900

Work is the success of the application force on an object which can produce displacement

θ

Displacement is considered

along the same

direction of applied force

A force at some angle (not 90A force at some angle (not 90OO) to the ) to the direction of movement can be resolved direction of movement can be resolved into the horizontal component to into the horizontal component to calculate the work done.calculate the work done.

Variation of work Variation of work with with θθ

W But When W= FSCos 90=0

Disp

lace

men

t

Scos θ

FORCE applied near the bottom

Scosθ

θ= 90

FORCE applied at the bottom line

S

Work is the success of the application force on an object which can produce displacement

θ Dis

plac

eme

nt

F

S

If θ

Negative work DoneNegative work Done

S cosθ θ> 90FORCE applied below C.G

1800 ≤ θ > 900

Work is the success of the application force on an object which can produce displacement

Displacement S

Force Direction

If θ>900 Then cosθ= -Ve so. Work = - Ve

Accepted Displacement

Negative work DoneNegative work Done

S cosθ θ = 18

00

FORCE applied below C.G

Work is the success of the application force on an object which can produce displacement

Force Direction

Accepted Displacement

When θ=1800 Then Work W= FS cos1800

W= FS(-1) = -Fs

This is Glen Canyon Dam on the This is Glen Canyon Dam on the Colorado River between Utah and Colorado River between Utah and Arizona. Arizona. The dam is among the tallest in The dam is among the tallest in America, so you can imagine the America, so you can imagine the tremendous pressure on the water tremendous pressure on the water as it moves to generators at the as it moves to generators at the bottom of the dam.bottom of the dam.

A Complete DefA Complete Defn.n. of of WORKWORK

The work done on an object is the magnitude of the applied force multiplied by the parallel distance* through which the force acts.Work = force X distanceW = Fs cosθ

Meaning of parallel Meaning of parallel distance…distance…the distance moved either in the same(θ=00) or opposite (θ=1800) direction of the applied force

or Part of the displacement (Scosθ) either same or opposite direction of the applied force

Be sure Be sure …..…..1. For a work Displacement is a must.

2. The part of the movement is considered either in the same or opposite direction of the applied force.

3. When force is resolved into the component force then only that part of force is considered which acts in the same direction of the displacement

Units of Units of Work:Work:

W = F SThe SI unit of WorkW = (Newton)(Meter)W = Nm = Joule

The The JouleJoule Joule (J): The SI unit of energy

Amount of work done by a force of one Newton when it acts through a distance of one meter:

Example: Push a box 8 m across the floor with a

force of 100 N performs 800 J of work:

m)(Nmeter .newton 1 (J) joule 1

JmNmNFdW 800800)8)(100(

H/W: CQa. What is zero work

b. Is there any work if you exchange 10 books in between the top shelf to the bottom shelf?

c. Calculate the work done to move a book of mass 1kg from 2nd shelf to 3rd shelf ?

d. Explain why work is a scalar quantity even though the force and displacement both are vector quantity

What is gravitational

work doneWhat is Mechanical

work done

Explain why work is a scalar quantity

Total height=2.5 mShelves are equally spaced

T HAN K S