DHS 03 Dynamics (Lecture Notes & Tutorial)

Dunman High School (Senior High Physics) Topic 3 – Dynamics GUIDING QUESTIONS  How do forces affect the motion of an object?  When is momentum conserved during interactions between objects?  How can we analyse interactions using he principle of momentum conservation? Content • Newton’s laws of motion • Linear momentum and its conservation Learning Outcomes Students should be able to: (a) state and apply each of Newton's laws of motion (b) show an understanding that mass is the property of a body which resists change in motion (inertia) (c) describe and use the concept of weight as the force experienced by a mass in a gravitational field (d) define and use linear momentum as the product of mass and velocity (e) define and use impulse as the product of force and time of impact (f) relate resultant force to the rate of change of momentum (g) recall and solve problems using the relationship F = ma, appreciating that resultant force and acceleration are always in the same direction (h) state the principle of conservation of momentum (i) apply the principle of conservation of momentum to solve simple problems including inelastic and (perfectly) elastic interactions between two bodies in one dimension (knowledge of the concept of coefficient of restitution is not required) (j) show an understanding that, for a (perfectly) elastic collision between two bodies, the relative speed of approach is equal to the relative speed of separation (k) show an understanding that, whilst the momentum of a closed system is always conserved in interactions between bodies, some change in kinetic energy usually takes place.

2 Dunman High School Year 5 Physics 2024/2025 0. Introduction In kinematics, we described motion in terms of displacement, velocity a nd acceleration. In this chapter, we investigate what causes change in motion. The relationship between a force and the acceleration it causes was first understood by Sir Isaac Newton (1642 – 1727). The study of the relationship is called Newtonian mechanics. In this topic, the focus is on Newton’s three laws of motion. Newtonian mechanics does not apply in the following situations:  When the speeds of the interacting bodies are very large (i.e. approaching the speed of light). In t his case, Einstein’s special theory of relativity replaces Newtonian mechanics.  When the interacting bodies are on the atomic scale. In this case, quantum mechanics replaces Newtonian mechanics. Physicists now view Newtonian mechanics as a special case of these two more comprehensive theories. 1. Newton’s Laws of Motion LO (a) state and apply each of Newton's laws of motion LO (b) show an understanding that mass is the property of a body which res ists change in motion (inertia) Newton's 1st Law of Motion states that: It is also known as the Law of Inertia. Inertia is a measure of the reluctance of an object to change its stat