Kinematics: equations of motion & projectiles
Kinematics is the study of motion — how we describe the way objects move using words, graphs and equations. In this Advanced Subsidiary lesson we carefully separate distance from displacement and speed from velocity, define acceleration as a vector, and learn to read a displacement–time graph (gradient = velocity) and a velocity–time graph (gradient = acceleration, area = displacement). We then DERIVE all four suvat equations of uniformly accelerated motion straight from a velocity–time graph, apply them to worked problems including free fall, meet the acceleration of free fall g and how to measure it, explain terminal velocity for a body falling with air resistance, and finally take a projectile apart into its independent horizontal and vertical components to see why its path is a parabola.
By the end you should be able to (NSSCAS Physics (AS) 1.3):
- Define and use distance, displacement, speed, velocity and acceleration, distinguishing scalar from vector quantities
- Distinguish instantaneous velocity from average velocity (total displacement ÷ total time)
- Use graphical methods to represent motion; determine velocity from the gradient of a displacement–time graph
- Determine acceleration from the gradient, and displacement from the area, of a velocity–time graph
- Recall the four equations of uniformly accelerated motion and derive them from the definitions of velocity and acceleration (a velocity–time graph)
- Solve problems using the suvat equations, including bodies falling freely in a uniform gravitational field without air resistance
- State the acceleration of free fall g and describe an experiment to determine it using a falling body
- Describe and explain qualitatively the motion of a body falling with air resistance, including terminal velocity
- Describe and explain motion due to a uniform velocity in one direction and a uniform acceleration in a perpendicular direction (projectile motion, parabolic path)
Miss Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.