Momentum and impulse

Nature of science:

The concept of momentum and the principle of momentum conservation can be used to analyse and predict the outcome of a wide range of physical interactions, from macroscopic motion to microscopic collisions. (1.9)

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

Applications and skills:

• Applying conservation of momentum in simple isolated systems including (but not limited to) collisions, explosions, or water jets
• Using Newton’s second law quantitatively and qualitatively in cases where mass is not constant
• Sketching and interpreting force–time graphs
• Determining impulse in various contexts including (but not limited to) car safety and sports
• Qualitatively and quantitatively comparing situations involving elastic collisions, inelastic collisions and explosions

• Automobile passive safety standards have been adopted across the globe based on research conducted in many countries

Theory of knowledge:

• Do conservation laws restrict or enable further development in physics?

Utilization:

• Jet engines and rockets

Martial arts

• Particle theory and collisions (see Physics sub-topic 3.1)

• Students should be aware that F = ma is equivalent of F = ∆p only when mass ∆t is constant
• Solving simultaneous equations involving conservation of momentum and energy in collisions will not be required
• Calculations relating to collisions and explosions will 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

Data booklet reference:

• Aim 3: conservation laws in science disciplines have played a major role in outlining the limits within which scientific theories are developed
• Aim 6: experiments could include (but are not limited to): analysis of collisions with respect to energy transfer; impulse investigations to determine velocity, force, time, or mass; determination of amount of transformed energy in inelastic collisions
• Aim 7: technology has allowed for more accurate and precise measurements of force and momentum, including video analysis of real-life collisions and modelling/simulations of molecular collisions