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Module 3:

Section 3.2 Forces in Action

3.2.1

Dynamics

(a) net force = mass × acceleration;

F = ma

This is often called Newton's Equation... it comes from his second law.

Learners will be expected to recall this equation.

(b) the newton as the unit of force

    

(c) weight of an object;

W = mg Learners will be expected to recall this equation.

(d) the terms tension, normal contact force, upthrust and friction

    

(e) free-body diagrams

    

(f) one- and two-dimensional motion under constant force.

    

3.2.2

Motion with non-uniform acceleration

(a) drag as the frictional force experienced by an object travelling through a fluid

   

(b) factors affecting drag for an object travelling through air

   

(c) motion of objects falling in a uniform gravitational field in the presence of drag

   

(d) (i) terminal velocity

(ii) techniques and procedures used to determine terminal velocity in fluids.

 

e.g. ball-bearing in a viscous liquid or cones in air.

Investigate factors affecting terminal velocity.
3.2.3 Equilibrium (a) moment of force    
(b) couple; torque of a couple    
(c) the principle of moments  

 
(d) centre of mass; centre of gravity; experimental determination of centre of gravity   See stability
(e) equilibrium of an object under the action of forces and torques  

For equilibrium:

Σ clockwise moments = Σ anticlockwise moments
(f) condition for equilibrium of three coplanar forces; triangle of forces.    

3.2.4

Density and pressure

 density = mass divided by volume ρ = m/V   
pressure; for solids, liquids and gases p = F/A  
upthrust on an object in a fluid; Archimedes' principle. p = hρg