Turning on a pivot

Turning on a pivot

IGCSE

​Learning Objectives

​• Know that forces can cause objects to turn on a pivot and understand the principle of moments.

• Select ideas and produce plans for testing based upon previous knowledge, understanding and research.

• Decide which measurements and observations are necessary and what equipment to use.

• Make observations and measurements.

• Choose the best way to present results.

• Describe patterns (correlations) seen in results.

• Interpret results using scientific knowledge and understanding.

• Draw conclusions.

​Glossary

​Balance : Seimbang

Distance : Jarak (m)

​Effort : Usaha

​Force : Gaya (N)

​Fulcrum : Titik Tumpu

​gear : gigi

​lever : Tuas

​​Moments : momen

​pivot : Poros/ Titik Tumpu

​Turning : Berputar

​Perpendicular : tegak lurus

​reduce : mengurangi

​Work : usaha

​

​Moments

​A moment is the turning effect of a force

• Moments occur when forces cause objects to rotate

  The moment of a force is given by :

               Moment (N m) = Force (N) × perpendicular distance from the pivot (m)

• The SI unit for the moment is Newton metres (Nm)

​A uniform metre rule is pivoted at the 50 cm mark. A 0.5 kg weight is suspended at the 80 cm mark, causing the rule to rotate about the pivot.

Assuming the weight of the rule is negligible, what is the turning moment about the pivot?

​Summary

​​A moment is the turning effect of a force

​The moment of a force is given by :

               Moment (N m) = Force (N) × perpendicular distance from the pivot (m)

Multiple Choice

What is the moment of a 6 N force acting 1.5 m from a pivot?

• 9 N/m

• 4 m

• 9 Nm

• 4 Nm

Multiple Choice

What is a moment?

• A lever

• The turning effect of a force

• A quantity detected by a multimeter

• A Gear

Multiple Choice

What is the unit of a moment?

• centimeter (cm)

• Newtons

• Newton per metre (N/m)

• Newtons-metre (Nm)

Levers​

A lever is a simple machine that makes work easier to do. Levers reduce the force needed to perform these tasks.​

​Types of Lever

Multiple Choice

How many classifications of lever systems are there?

• 1

• 2

• 3

• 4

Multiple Choice

What type of lever, useful for overcoming large loads, can be found at the ankle when a basketball player jumps for a rebound?

• first class lever

• second class lever

• third class lever

• no lever

Multiple Choice

what type of lever useful for the picture?

• first class lever

• second class lever

• third class lever

• no lever

​Principal of moment

​Balancing moments

Where an object is not turning around a pivot, the total clockwise moment must be exactly balanced by the total anti-clockwise moment. We say that the opposing moments are balanced:

sum of the clockwise moments = sum of the anti-clockwise moments

​Balancing ACT

​what makes the pictures different?

sum of the clockwise moments = sum of the anti-clockwise moments

​M clockwise= M anti-clockwise

​M right = M left

​F. d (right)= F. d (left)