Section 1 – pg 338 Describing Motion Chapter 9 Section 1 – pg 338 Describing Motion

Pg 339 Motion An object is in motion if its distance from another object is changing

Pg 339 Reference Points Reference Point: a place or object used for comparison to determine if something is in motion Indicate a change in position by using plus and negative signs IE: 5 feet ahead (+5) 5 feet behind (-5)

Pg 340 Relative Motion Depending on your reference point you may or may not be moving Sitting in chair reading book: If your chair is the reference point then you are not moving If the sun is your reference point then you are moving quite fast

Distance and Displacement Pg 340 Distance and Displacement Distance: the length of a path between two points The total length of the actual path between two points Displacement: the length and direction that an object has moved from its starting point The length and direction of a straight line between starting and ending points

Vector: a quantity that consists of both a magnitude and a direction Displacement, acceleration, velocity, force Vectors are shown graphically by using an arrow The length of the arrow represents the vector’s magnitude The direction of the arrow indicates the direction of the vector Pg 341

Chapter 9 Section 1 Homework Pg 341

1A. How do you know if an object is moving?

1B. Why is it important to know if your reference point is moving?

1C. Suppose you are riding in a car 1C. Suppose you are riding in a car. Describe your motion relative to the car, to the road, and to the sun.

2A. What is displacement?

2B. How are distance and displacement similar? How are they different?

2C. An object moves 3 cm to the right, then 6 cm to the left, then 8 cm to the right. What is the object’s final displacement from its origin? 3 cm 6 cm 8 cm