Module 2: Dynamics
NSW HSC Physics Year 11
Module Overview
Dynamics extends kinematics by examining the forces that cause motion. This module covers Newton’s Laws of Motion, momentum, energy, and their applications to real-world situations.
Indicative Hours: 30 hours
Related Outcomes:
- PH11-8 describes and analyses motion in terms of scalar and vector quantities
- PH11-9 describes and explains events in terms of Newton’s Laws of Motion, conservation of momentum and conservation of energy
Inquiry Questions
How are forces produced between objects and what effects do forces produce?
How can the motion of objects be explained and analysed?
Key Concepts
2.1 Forces
Learning Focus
Understand the nature of forces and apply Newton’s Laws to analyse motion.
Content:
- Identify forces acting on objects using free-body diagrams
- Apply Newton’s three laws of motion to solve problems
- Analyse equilibrium conditions for objects at rest and in motion
- Calculate friction forces and understand their role in motion
Newton’s Laws:
| Law | Statement | Formula |
|---|---|---|
| First Law | An object remains at rest or in uniform motion unless acted upon by a net force | If \(\Sigma F = 0\), then \(a = 0\) |
| Second Law | Acceleration is proportional to net force and inversely proportional to mass | \(\Sigma F = ma\) |
| Third Law | For every action there is an equal and opposite reaction | \(F_{AB} = -F_{BA}\) |
2.2 Momentum
Learning Focus
Apply the law of conservation of momentum to collision and explosion problems.
Content:
- Define momentum and impulse
- Apply the law of conservation of momentum
- Analyse elastic and inelastic collisions
- Solve problems involving explosions and recoil
Key Formulas:
| Quantity | Formula |
|---|---|
| Momentum | \(p = mv\) |
| Impulse | \(J = F\Delta t = \Delta p\) |
| Conservation of momentum | \(m_1u_1 + m_2u_2 = m_1v_1 + m_2v_2\) |
2.3 Energy
Learning Focus
Apply energy concepts and the law of conservation of energy to mechanical systems.
Content:
- Calculate kinetic energy and gravitational potential energy
- Apply the law of conservation of mechanical energy
- Analyse energy transformations in mechanical systems
- Calculate work done by constant and variable forces
Key Formulas:
| Quantity | Formula |
|---|---|
| Kinetic energy | \(E_k = \frac{1}{2}mv^2\) |
| Gravitational PE | \(E_p = mgh\) |
| Work | \(W = Fs\cos\theta\) |
| Power | \(P = \frac{W}{t} = Fv\) |
Working Scientifically
Practical Investigations
- Newton’s Second Law
- Investigate the relationship between force, mass, and acceleration
- Use dynamics trolleys and motion sensors to collect data
- Conservation of Momentum
- Analyse collisions between objects of different masses
- Compare elastic and inelastic collisions
- Energy Transformations
- Investigate energy changes in pendulum motion
- Analyse efficiency of energy transformations
Key Definitions
- Force
- A push or pull that can change the motion of an object; measured in newtons (N).
- Net Force
- The vector sum of all forces acting on an object.
- Momentum
- The product of mass and velocity; a vector quantity measured in kg·m/s.
- Impulse
- The product of force and time; equal to the change in momentum.
- Kinetic Energy
- The energy an object possesses due to its motion.
- Potential Energy
- Stored energy due to position or configuration.
- Work
- The energy transferred when a force moves an object; measured in joules (J).