8.3 Moving About

1. 8.3 Moving About Part 1: Basic concepts in Motion

2. Identify that a typical journey involves speed changes • Define average velocity as: vav= r/t • Solve problems and analyse information using the formula: vav= r/t where r = displacement • Distinguish between scalar and vector quantities in equations • Describe the motion of one body relative to another • Distinguish between the average and instantaneous speed of vehicles and other bodies • Compare instantaneous and average speed with instantaneous and average velocity • Plan, choose equipment or resources for, and perform a first-hand investigation to measure the average speed of an object or a vehicle • Present information graphically of displacement vs time and velocity vs time graphs for objects with uniform and non-uniform linear velocity The Objectives

3. Scalars: any quantity that has magnitude only eg: time, energy, distance, speed • Vectors: quantities that have both magnitude and direction eg: displacement, velocity, acceleration, force • For vector quantities, you MUST specify a direction if it is at all possible. • Vectors are often typed in bold or with an arrow abo them • A minus sign in front of a vector quantity is a symbol meaning “in the opposite direction” The First Idea: Scalars vs Vectors

4. Compass bearings: • True Bearings: Bearings: A Quick Reminder

5. Vectors can be represented using an arrow. • The length of the arrow is an indication of the magnitude (or size) of the vector. • The direction of the arrow indicates the direction of the vector Representing Vectors

6. Distance is how far something has actually travelled. The symbol for distance is d • Displacement is how far the object is from where it started, and the direction that the object would have had to travel from the starting point to get there directly. The symbol for displacement is r (or s) Introducing displacement

7. Average Speed is defined as “the rate of change of distance”. • The equation is s = Dd/Dt • Average Velocity is defined as “the rate of change in displacement • The equation is v = Dr/Dt • Note that D means “change in” or final value minus initial value. Introducing Velocity

8. Average vsInstantaneous

9. Vectors cannot just be added like scalars, since there is a direction involved as well. • Think about someone running 4m West and then 6m East. They are not 10m from their starting point. • The resultant (or final displacement) is 2m East of the starting point 4 m West 2 m East 6 m East Vector addition

10. Mathematical • Components Methods for adding vectors

11. Defined as how fast you are going (and in what direction) compared to some other point (Actually, all velocities are relative but if it is being measured relative to the ground, we don’t take any notice of it!) • The velocity of object A relative to object B is given the symbol vAB • The formula is vAB = vA – vB • Note that you have to subtract the vectors using vector “addition”! Relative Velocity

12. Defined as how fast your velocity is changing. a = Dv/Dt Two important things to note: • Acceleration is a vector quantity so you need to give a direction if possible • A change in direction is a change in velocity and therefore an acceleration. Acceleration