# 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.

## Presentation on theme: "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."— Presentation 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 Systems Mainly 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 Revision Weight (N) = mass (kg) x gravity (m/s 2 ) 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)

Pulleys Where 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/s 2 ) Bucket weight = 20kg x 10m/s 2 = 200 N Weight = 200N Force required to lift bucket = 200N

How do pulleys work? Simple pulley : 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

Mechanical Advantage = ÷ 200N 200N Force In – person pulls rope Force Out – force to lift bucket upwards Force In Mechanical Advantage Force Out = ÷ 200 N 1

Mechanical Advantage = ÷ 200N 100N Force In – person pulls rope Force Out – force to lift bucket upwards Force In Mechanical Advantage Force Out = ÷ 100 N 2 200 N

Shortcut! = x Number of movable pulleys Mechanical Advantage 2 200N 50N Force In – force in rope Weight Static Pulleys Movable Pulleys = x 2 4 2

Mechanical Advantage = ÷ 200N 50N Force In – force in rope Force Out – force to lift bucket upwards Force In Mechanical Advantage Force Out = ÷ 50 N 4 200 N 4 ropes Force In Rope = 200 ÷ 4 Weight Total Force to lift bucket upwards 50N 50N 50N 50N 200N

= x Shortcut! Force In Force Out Mechanical Advantage 200N 50N Force In – pull on rope Force Out – force to lift bucket Static Pulleys 2 Movable Pulleys 50N 200N 4

Let us play a game !!! I am owner of a car manufacturing company I will need one big shutter for security purpose Shutter weight will be 1000KG I want to have a solution that will allow the gate to be opened only from inside I do not want to spend too much money on it Extra points for creativity and good presentation!

Conditions Group of 4 Decide your team leader 10 mins –Plan your idea 20 mins – Load calculation 30 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 itemMass per item Pulley1000 rupees10 kg Multi- Pulley 2000 rupees20 kg Cost per metre Rope50 rupees Cost of electric winchPulling force of winch Winch6000 rupees2000 N Mass of Door Door1000 kg वजन (N) = वस्तुमान (kg) x गुरुत्वाकर्ष Mechanical Advantage = 2 x number of movable pulleys