H1.02. 2022 Kinematics Notes

CJC H1 PHYSICS LECTURE NOTES JC1 2022 2(1) 2 Kinematics Main concept(s) 1. Rectilinear Motion 2. Non-Linear Motion (including Projectile Motion) Learning Outcome(s) Candidates should be able to: (a) show an understanding of and use the terms 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 displacement -time graphs and areas 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, including the motion of bodies falling in a uniform gravitational field without air resistance. (f) describe qualitatively the motion of bodies falling in a uniform gravitational field with air resistance. (g) describe and explain motion due to a uniform velocity in one direction and a uniform acceleration in a perpendicular direction. ~ Introduction Today, we use electronic stopwatches, video recorders and other sophisticated instruments to analyse motion, but it has not always been so. Galileo, who in the early 1600s was the first scientist to study motion experimentally, used his pulse to measure time! Galileo made a useful distinction between the cause of motion and the description of motion. “Kinematics” is the modern term for the mathematical description of motion without regard to causes. The term comes from the Greek word kinema, meaning “movement ”. This chapter begins with visualising motion and developing the representations for describing the positio n, displacement, velocity and acceleration of moving objects in space as a function of time . We will begin our study of kinematics with motion in one dimension, followed by two dimensions. Essential Questions • How do we describe the motion of objects? • How can the motion of objects be represented, quantified and predicted? • How can we tell if an object is moving with a constant acceleration? • How would an object experiencing constant acceleration in one direction and constant velocity in a perpendicular direction move? • How would an object falling in a uniform gravitational field move?

CJC H1 PHYSICS LECTURE NOTES JC1 2022 2(2) 1. 2.1 RECTILINEAR MOTION Rectilinear motion means motion in a straight line. 2.1.1 Displacement vs Distance Example 1 Consider a car moving to the left. The positions of the car at various instan ces in time t are represented as dots in a straight line. This straight line serves as a reference to a coordinate axis, just like the x-axis. To make the discussion of displacement meaningful, ❖ A reference point must be defined. For example, o If t = 0 s is