chapter 5 turning effect of forces

What is a moment?

• also known as torque

• turning effect of a force

• M=fd

f→ force

d→ perpendicular distance from the pivot to line of action of force

When does a force cause something to turn?

** must also remember to convert g to kg

** BE careful of units

Example of using a lever

longer spoon → further perpendicular distance from pivot to line of action of force → larger moment applied → easier to lift lid

line of action of force

line of action of a force is straight line through a point where a force applied follows the direction of that force vector

• extend horizontally/vertically towards the direction of arrow of force applied

• pivot can extend accordingly to meet line of action

• use ruler to draw

Conditions required for objects to remain balanced

conditions for equilibrium

centre of gravity

example

** centre of gravity can be for both balanced/unbalanced object

** every object has a centre of gravity

position of centre of gravity

position of centre of gravity to be balanced/unbalanced

Concept: moment= force x perpendicular distance from pivot to line of action of force

1. The perpendicular distance from pivot to line of action of force increases/decreases

2. since moment = force x perpendicular distance, clockwise/anticlockwise moments about (the pivot) increases/decreases

concept : line of action falls outside or within base area

1. base area becomes larger/smaller OR CG is raised/lowered

2. line of action of force falls outside/within base area, resulting in a clockwise/anticlockwise moment

3. object will topple/will not topple

reminders