NJC Unit 2 Forces and Moments

National Junior College Science Department | Physics 1 2. Forces & Moments Content Page 2.1 Types of forces ................................ ................................ ................................ .....................3 2.1.1 What is a force? ................................ ................................ ................................ ...........3 2.1.2 Contact forces ................................ ................................ ................................ .............4 2.1.3 Fields of forces ................................ ................................ ................................ ............6 2.1.4 Hooke’s law ................................ ................................ ................................ .................7 Compressive and tensile force ................................ ................................ .............................7 Hooke’s law ................................ ................................ ................................ .........................8 2.2 Drawing force diagrams ................................ ................................ ................................ .15 2.3 Moment and Torque ................................ ................................ ................................ ......20 2.3.1 Moment of a force ................................ ................................ ................................ ......20 2.3.2 Torque of a Couple ................................ ................................ ................................ ....24 2.4 Translational and rotational equilibrium ................................ ................................ .........28 2.4.1 Principle of moments ................................ ................................ ................................ .28 2.4.2 Centre of gravity ................................ ................................ ................................ ........29 2.4.3 Equilibrium ................................ ................................ ................................ .................30 2.5 Upthrust (H2 Physics only) ................................ ................................ ........................38

National Junior College Science Department | Physics 2 Learning Objectives 2.1 Types of forces (a) Describe the forces on a mass, charge and current -carrying conductor in gravitational, electric and magnetic fields, as appropriate. (b) H2: Show a qualitative understanding of forces including normal force, frictional force, buoyant force (upthrust), and viscous force, e.g. air resistance (knowledge of the concepts of coefficients of friction and viscosity is not required). H1: Show a qualitative understanding of forces including normal force, frictional force and viscous force, e.g. air resistance (knowled ge of the concepts of coefficients of friction and viscosity is not required). (c) Recall and apply Hooke’s law ( 𝐹 = 𝑘𝑥, wher