2. Mechanics

InThinking Physics UN: Cooper and PW: slphysics

2.1 MOTION

Understandings:

Determine instantaneous and average blues for velocity, speed and acceleration
Solve problems using equations of motion for uniform acceleration (suvat)
Sketch and interpret motion graphs
Determine the acceleration of free fall experimentally
Analyse projectile motion, include the resolution of vertical and horizontal components of acceleration, velocity and displacement
Qualitatively describe the effect of fluid resistance on falling objects or projectiles, including reaching terminal speed

Applications and skills:

Diving and parachuting
Ballistics
Biomechanics
Quadratics

Guidance:

Calculations will be restricted to those neglecting air resistance
Projectile motion problems will only include values of g (9.81 m/s2)

Utilization:

Diving and parachuting
Ballistics
Biomechanics
Quadratics

Data booklet reference:

Practice and review:

2.1 SLIDES

2.1 Problem Set 1

2.1 Problem Set 1 solns

2.2 FORCES

Understandings:

Objects as point particles
Free-body diagrams
Translational equilibrium
Newton’s laws of motion
Solid friction

Applications and skills:

Represent forces as vectors
Sketch and interpret free body diagrams
Describe the consequences of Newton’s first law for translational equilibrium
Use Newton’s second law quantitatively and qualitatively
Identify force pairs in the context of Newton’s third law
Solve problems involving forces and determine resultant force
Describe solid fiction (static and dynamic) by coefficients of friction

Guidance:

Students should label forces using commonly accepted names or symbols (ex. weight or force of gravity or mg)
Free-body diagrams should show scaled vector lengths acting from the point of application
Questions will be limited to constant mass
mg should be identified as weight
Calculations related to the determination of resultant forces will be limited to one- and two-dimensional situations

Utilization:

Motion of charged particles
Application of fiction in circular motion
Construction
Biomechanics

Data booklet reference:

Practice and review:

2.3 WORK, ENERGY AND POWER

Understandings:

Kinetic energy
Gravitational potential energy
Elastic potential energy
Work done as energy transfer
Principle of conservation of energy
Efficiency

Applications and skills:

Discuss the conservation of energy within energy transformations
Sketch and interpret force-distance graphs
Determine work done include case where a resistive force acts
Solve problems involving power
Quantitatively describe efficiency in energy transfers

Guidance:

Cases where the line of action of the force and the displacement are not parallel should be considered
Examples should include force-distance graphs for variable forces

Utilization:

Energy is also covered in other group 4 subjects
Energy conversions are essential for electrical energy generation
Energy changes occurring in simple harmonic motion

Data booklet reference:

Practice and review:

Hooke's Law Simulation on Phet
LoggePro graph - finding the spring constant

Hooke's Law PHET

Hooke's Law LoggerPro

2.4 MOMENTUM AND IMPULSE

Understandings:

Newton’s second law expressed in terms of rate of change in momentum
Impulse and force-time graphs
Conservation of linear momentum
Elastic collision, inelastic collisions, and explosions

Applications and skills:

Apply conservation of momentum in simple isolated systems including (but not limited to) collisions, explosions or water jets
Use Newton’s second law quantitatively and qualitatively in cases where mass is not constant
Sketch and interpret force-time graphs
Determine impulse in various contexts including (but no limited to) car safety and sports
Qualitatively and quantitatively compare situations involving elastic collisions, inelastic collisions and explosions

Guidance:

F = ma is equivalent to F = p/t only when mass is constant
Calculations relating to collisions and explosions will only be restricted to one-dimensional situations
A comparison between energy involved in inelastic collisions (in which kinetic energy is not conserved) and the conservation of (total) energy should be made

Utilization:

Jet engines and rockets
Particle theory and collisions in martial arts

Data booklet reference:

Practice and review: