【国际物理】【预备课程】IGCSE力矩和力矩平衡MOMENTS

1A 4 MOMENTS 力矩 Levers are almost everywhere in our daily life. straw chopper bottle opener What is the principle of levers? 01. Calculate the moment of a force 02. 03. LEARNING OBJECTIVE CONTENTS Apply the Principle of moments Find the centre of gravity of an object “Give me a fulcrum, I can pry to move the Earth!”——Archimedes 1、THE MOMENT OF A FORCE ①c oncept ：The turning effect of a force is called its moment. ②Formula： moment (N m)＝force(N) × perpendicular distance from the pivot to the line of action of the force（m） moment ＝ F × x ③the SI Unite：N m 1、THE MOMENT OF A FORCE example 1. A student pulls down with a force of 40N on a rope, that winds arould the pulley of radius of 5cm, what is the moment of the force? moment =F × r =40 × 0.05 =2Nm 2、THE PRINCIPLE OF MOMENTS Force 1×Arm of Force 1=Force 2×Arm of Force 2 F1×l1=F2×l2 F1 F2 l1 o l2 2、THE PRINCIPLE OF MOMENTS ①remain stationary ②rotate at the same speed in the same direction 2、THE PRINCIPLE OF MOMENTS F1×l1=F2×l2+F3×l3 2、THE CENTRE OF GRAVITY 2、THE CENTRE OF GRAVITY REGULAR OBJECTS ①with an even weight distribution ②with a regular Geometric shape We can find the gravity cetre at geometrical center. 2、THE CENTRE OF GRAVITY IRREGULAR OBJECTS