Section 4.1 Speed & Velocity

1. Section 4.1Speed & Velocity • What is motion? • A change in the position of an object relative to another object (a reference point), which is assumed to be at rest. • Uniform motion is when an object moves in a straight line at constant speed. • We describe an object’s motion by talking about its . . . • Speed – how quickly something moves.

2. Section 4.1Speed & Velocity • How would you try to calculate the speed of a moving object? • Speed = distance object moves time it takes to move there speed (v) = d (distance) t (time)

3. Section 4.1Speed & Velocity • The units for speed are distance units over time units. • What units are commonly used to describe distance and time? :

4. Section 4.1Speed & Velocity • Average Speed: • When you divide the total distance of the trip by the total time taken.

5. Section 4.1Speed & Velocity • Instantaneous speed: • The actual speed an object has at any given moment. • What is an example of a device that gives instantaneous speed? • Car speedometer

6. Section 4.1Speed & Velocity • Velocity (v): • Speed WITH direction. Velocity is a vector. • Vector – a variable that has magnitude (or a number) and adirection. +65 m/s East -65 mph West

7. Section 4.1Speed & Velocity So … What’s The Difference? • Speed or Velocity?: 1) Johnny drove to work travelling 75 mph east. ~ VeLoCiTy 2) Alicia walks 5 mph every day to get to her middle school. ~ SpEeD

8. Section 4.1Speed & Velocity • Solving Problems With Speed: How far do you go if you drive for 2 hours at a speed of 100 km/h? • Looking for? ... Distance • Given?… speed = 100 km/h time = 2 h • Relationships? • d = v x t • Solution? • d = 100 km/h x 2 h = 200 km = 200 km