Moments And Levers P
Overview
Try to shut a heavy door by pressing on it a centimetre from the hinges. You will push until your arm aches and the door will barely shift. Move your hand out to the handle, use a fraction of that effort, and the door swings closed. Nothing about the door has changed and nothing about your strength has changed. What changed is the distance, and distance is the second half of every turning problem in physics.
This lesson gives you the quantity that measures a turn: the moment of a force, worth force multiplied by perpendicular distance, measured in newton metres. You will use it to balance a beam by setting the clockwise turns against the anticlockwise ones, to work out an unknown force or an unknown distance from that balance, to predict the exact moment a crate or a bus stops leaning and starts falling, and to explain how a crowbar lets a pair of hands move a boulder that no pair of hands could ever lift.
Objectives
- The turning effect of a force is called the moment. The relationship between the moment, M, turning force, F, and perpendicular distance, d, from the point where the force is applied to the pivot is: M = F ×d
- If an object is not turning, the total clockwise moment must be exactly balanced by the total anticlockwise moment about any pivot. Students should be able to calculate the size of a force, or its distance from a pivot, acting on an object that is balanced.
- If the line of action of the weight of an object lies outside the base of the object there will be a resultant moment and the body will topple. Examples should include vehicles and simple balancing toys.
- Simple levers can be used as force multipliers.
Mind map
This topic is mapped out so you can see how the ideas connect.
Open the mind map in the app
Lesson Note
Complete Note Available on the Green Bridge App
Get the Green Bridge CBT app on your phone or computer for the complete IGCSE library: past papers, mark schemes, mind maps, flashcards and audio lessons.
Lesson Evaluation
Congratulations on completing the lesson on Moments And Levers P. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- What is the unit of the moment of a force? A. newton B. newton metre C. newton per metre D. metre Answer: B
- A force of 25 N acts at a perpendicular distance of 0.40 m from a pivot. What is the moment of the force about the pivot? A. 0.016 N m B. 10 N m C. 25.4 N m D. 62.5 N m Answer: B
- A beam is pivoted at its centre. A force of 60 N acts 0.50 m to the left of the pivot. A force F acts 0.25 m to the right of the pivot and the beam is balanced. What is F? A. 30 N B. 60 N C. 120 N D. 240 N Answer: C
- An object standing on a flat surface will topple when A. its weight is greater than the contact force from the surface B. the line of action of its weight lies outside its base C. its centre of mass is above the middle of its base D. the clockwise and anticlockwise moments about its edge are equal Answer: B
- A crowbar allows a small effort to move a much larger load. This is because a simple lever acts as a A. distance multiplier B. energy multiplier C. force multiplier D. speed multiplier Answer: C
Work through these questions in the app
Work through these questions in the app
Recommended Books
Practice Mock Questions
Want to practice mock questions on Moments And Levers P? Download the Green Bridge CBT app to access mock questions and full practice assessments for this topic.
Download The App On Google Playstore
Everything you need to excel in your exams
