what is pulley ? pulley : it is a simple machine made up of a wheel and a rope. wheel is nothing but...
TRANSCRIPT
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)
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
Thanks
For further information: Website : www.vigyanashram.come-Mail : [email protected], [email protected]
Thanks
For further information: Website : www.vigyanashram.come-Mail : [email protected], [email protected]