What is Pulley ?Pulley : It is a simple machine made up of a wheel

and a rope. Wheel is nothing but a grooved rim around which a cord passes. The rope fits into the wheel and one end of the rope is attached to the load.When you pull on one side of the pulley, the wheel turns and the load moves.

Why do we use it?-We use pulleys because they help to move loads up, down or sideways. -They are widely used for moving objects in hard to reach places. 

- They can also be used to provide power from one shaft to another.

Types of Pulley SystemsMainly there are two types :

Fixed : A fixed pulley has an axle mounted in bearings attached to a supporting structure

Movable : A movable pulley has an axle in a movable block

Quick RevisionWeight (N) = mass (kg)

x gravity (m/s2)

pivot

1 m 2 m

? kg 60 kg

•Big distance

•Small force

•Small distance

•Big force

30 kg

Moment (Nm) = Force (N) x distance from pivot (m)

PulleysWhere pulleys are used ?

How do pulleys work?Let us take an example to understand The functionality of pulley.

For example -We want to lift a 20 kg bucket of water.So weight would be :-

Weight (N) = mass (kg) x gravity (m/s2)

Bucket weight = 20kg x 10m/s2

= 200 N

Weight = 200N

Force required to lift bucket = 200N

How do pulleys work? Simple pulley :

200N

200N

Force In – person pulls rope

Force Out – force to lift bucket upwards

Force In Rope – force is constant along length

Force In = Force Out

( 200 N = 200N ) Pulley video 1

How do pulleys work?Simple Pulley:

200N

100N

Force In – person pulls rope

Force Out – force to lift bucket upwards

Force In Rope – force is constant along length at 100N

Force Out is more than Force In! •Pulley video 2

Total force to lift bucket upwards

200N

Weight of bucket

Force in each end of rope needed to lift bucket

100N

100N

100N

Mechanical Advantage = ÷

200N200N

Force In – person pulls rope

Force Out – force to lift bucket upwards

Force InMechanical Advantage Force Out

= ÷ 200 N1 200 N

Mechanical Advantage = ÷

200N

100N

Force In – person pulls rope

Force Out – force to lift bucket upwards

Force InMechanical Advantage Force Out

= ÷ 100 N2 200 N

Shortcut! = x Number of movable

pulleysMechanical Advantage 2

200N

50N

Force In – force in rope

Weight

Static Pulleys

Movable Pulleys

= x 24 2

Mechanical Advantage = ÷

200N

50N

Force In – force in rope

Force Out – force to lift bucket upwards

Force InMechanical Advantage Force Out

= ÷ 50 N4 200 N

•4 ropes

•Force In Rope = 200 ÷ 4

Weight

Total Force to lift bucket upwards

50N50N50N50N200N

= x

= x

Shortcut!Force InForce Out Mechanical Advantage

200N

50N

Force In – pull on rope

Force Out – force to lift bucket

Static Pulleys

2 Movable Pulleys

50N200N 4

Let us play a game !!!I am owner of a car manufacturing companyI will need one big shutter for security

purposeShutter weight will be 1000KGI want to have a solution that will allow the

gate to be opened only from insideI do not want to spend too much money on itExtra points for creativity and good presentation!

ConditionsGroup of 4Decide your team leader10 mins –Plan your idea20 mins – Load calculation30 mins- Design work – (door, pulley, using space

efficiently )20 mins - Working on business aspect – Why

someone should choose your idea? Ensure that you can convince mathematically .

Points will be calculated based on :-- “load calculation” only if it is accurate, new ideas, creative thinking, business logic, and neat presentation

Winner will get a price !!!

Business Game!

Mechanical Advantage = Force Out (N) ÷ Force In (N)

Cost per item Mass per item

Pulley 1000 rupees 10 kg

Multi-Pulley

2000 rupees 20 kg

Cost per metre

Rope 50 rupees

Cost of electric winch Pulling force of winch

Winch 6000 rupees 2000 N

Mass of Door

Door 1000 kg

वजन (N) = वस्तु�मा�न (kg) x गु�रुत्व�कर्ष�

Mechanical Advantage = 2 x number of movable pulleys

Business Game!

Few ideas

Thanks

For further information: Website : www.vigyanashram.come-Mail : vapabal@gmail.com, director@vigyanashram.com

Thanks

For further information: Website : www.vigyanashram.come-Mail : vapabal@gmail.com, director@vigyanashram.com