RI Chap 3 Motion and Forces Lecture Notes

3 MOTION & FORCES H2 Physics 9478 Content Page 3.1 Kinematics 2 3.2 Uniformly accelerated linear motion 5 3.3 Mass and linear momentum 11 3.4 Newton’s Laws of motion 12 Learning Outcomes Candidates should be able to: (a) show an understanding of and use the terms position, distance, displacement, speed, velocity, and acceleration. (b) use graphical methods to represent distance, displacement, speed, velocity, and acceleration. (c) identify and use the physical quantities from the gradients of position- time or displacement-time graphs, and areas under and gradients of velocity -time graphs, including cases of non- uniform acceleration. (d) derive, from the definitions of velocity and acceleration, equations which represent uniformly accelerated motion in a straight line. (e) solve problems using equations which represent uniformly accelerated motion in a straight line, e.g. for bodies falling vertically without air resistance in a uniform gravitational field. (f) show an understanding that mass is the property of a body which resists change in motion (inertia). (g) define and use linear momentum as the product of mass and velocity. (h) state and apply each of Newton’s laws of motion: 1st law: a body at rest will stay at rest, and a body in motion will continue to move at constant velocity, unless acted on by a resultant external force; 2nd law: the rate of change of momentum of a body is (directly) proportional to the resultant force acting on the body and is in the same direction as the resultant force; and 3rd law: the force exerted by one body on a second body is equal in magnitude and opposite in direction to the force simultaneously exerted by the second body on the first body. (i) recall the relationship resultant force 𝐹𝐹 = 𝑚𝑚𝑚𝑚 for a body of constant mass, and use this to solve problems.

Pag e | 2 3.1 Kinematics  Introduction The study of the motion of objects, with the associated concepts of force and energy, is called mechanics. Mechanics can be further divided into two parts: 1. kinematics which describe how objects move and 2. dynamics which deal with force and why objects move as they do. Motion can be categorized into three types: • translational, • rotational and • vibrational. In this chapter, we are concerned only with translational motion and will treat the moving object as a particle, regardless of its size. Strictly speaking, a particle is a point -like object with mass but no size. However, we can still apply the particle model to objects such as a ball or a car, provided the positions of the objects refer to their centres of mass. We begin our study with rectilinear motion , which is motion in one dimension or motion in a straight line, and then proceed to projectile motion, which is an example of motion in a two-dimensional plane. Circular motion is another example of motion in a plane and that will be covered in a later chapter. All measurements of distanc