Dynamics

This lesson comprises eight (8) master classes focusing on:

• Forces between objects
• Newton's laws
• Momentum
• Interactions and collisions

Content:

PH11-9

How are forces produced between objects and what effects do forces produce?

• Using Newton’s Laws of Motion, describe static and dynamic interactions between two or more objects and the changes that result from:
  • a contact force
  • a force mediated by fields
• Explore the concept of net force and equilibrium in one-dimensional and simple two-dimensional contexts using:
  • algebraic addition
  • vector addition
  • vector addition by resolution into components
• Solve problems or make quantitative predictions about resultant and component forces by applying the following relationships:
  • \( \vec{F}_{AB}=−\vec{F}_{BA} \)
  • \( F_x=F \cos \theta \), \(F_y=F \sin \theta \)
• Conduct a practical investigation to explain and predict the motion of objects on inclined planes

How can the motion of objects be explained and analysed?

• Apply Newton’s first two laws of motion to a variety of everyday situations, including both static and dynamic examples, and include the role played by friction \( \vec{f}_{friction}=\mu \vec{F}_N \)
• Investigate, describe and analyse the acceleration of a single object subjected to a constant net force and relate the motion of the object to Newton’s Second Law of Motion through the use of:
  • qualitative descriptions
  • graphs and vectors
  • deriving relationships from graphical representations including \( \vec{F}_{net}=m \vec{a} \) and relationships of uniformly accelerated motion
• Apply the special case of conservation of mechanical energy to the quantitative analysis of motion involving: 
  • work done and change in the kinetic energy of an object undergoing accelerated rectilinear motion in one dimension \( W=F_{\parallel}s=Fs \cos \theta \)
  • changes in gravitational potential energy of an object in a uniform field \( \bigtriangleup U=mg \bigtriangleup h \)
• Conduct investigations over a range of mechanical processes to analyse qualitatively and quantitatively the concept of average power \( P=\frac{\bigtriangleup E}{\bigtriangleup t} \), \( P=F_{\parallel}v=Fv \cos \theta \) including but not limited to:
  • uniformly accelerated rectilinear motion
  • objects raised against the force of gravity
  • work done against air resistance, rolling resistance and friction

How is the motion of objects in a simple system dependent on the interaction between the objects?

• Conduct an investigation to describe and analyse one-dimensional (collinear) and two-dimensional interactions of objects in simple closed systems
• Analyse qualitatively and predict, using the law of conservation of momentum \( \sum m \vec{v}_{before}= \sum m \vec{v}_{after} \) and, where appropriate, conservation of kinetic energy \( \sum \frac{1}{2} mv^2_{before}=\sum \frac{1}{2} mv^2_{after} \), the results of interactions in elastic collisions
• Investigate the relationship and analyse information obtained from graphical representations of force as a function of time
• evaluate the effects of forces involved in collisions and other interactions, and analyse quantitatively the interactions using the concept of impulse \( \bigtriangleup \vec{p}=\vec{F}_{net} \bigtriangleup t \)
• Analyse and compare the momentum and kinetic energy of elastic and inelastic collisions

PH11-2

• Assess risks, consider ethical issues and select appropriate materials and technologies when designing and planning an investigation
• Justify and evaluate the use of variables and experimental controls to ensure that a valid procedure is developed that allows for the reliable collection of data
• Evaluate and modify an investigation in response to new evidence

PH11-4

• Select qualitative and quantitative data and information and represent them using a range of formats, digital technologies and appropriate media
• Apply quantitative processes where appropriate
• Evaluate and improve the quality of data

PH11-6

• Use modelling (including mathematical examples) to explain phenomena, make predictions and solve problems using evidence from primary and secondary sources
• Use scientific evidence and critical thinking skills to solve problems