Physical Science 11.1 Motion

Question How fast do you think we are traveling (orbiting) around the sun? 67,062 mph How fast do you think we are spinning around our axis as we move around the sun? 1,041.67 mph Why don’t we feel this motion?

Frame of Reference To describe motion accurately, a frame of reference is necessary. Frame of Reference is a system of objects that are not moving with respect to one another

Frame of Reference Motion is a change in position relative to a frame of reference Relative Motion Movement in the relation to a frame of reference

Frame of Reference Example: Train moving past a platform with passengers standing on the platform looking at the train speeding by.

What is Motion? Question If you are standing in one place, and your friend walks by you: Are you moving relative to your friend? Is your friend moving relative to you? Are you moving relative to the earth? Is your friend moving relative to the earth? Is either of you moving relative to the sun?

What is Motion? Answers You are moving relative to your friend Your friend is moving relative to you! You are not moving relative to the earth Your friend is moving relative to the earth You are both moving relative to the sun

What is needed to describe motion accurately? Frame of Reference

Distance vs. Displacement

Distance Distance The length of the path between two points. Units for Distance Meters (m) or Kilometers (Km)

Displacement Displacement The direction from the starting point and the length of the straight line from the starting point to the ending point. Example: Think about the motion of a roller coaster car. Describe the distance the coaster moved. The path along which the car travelled What would the displacement be for a roller coaster? Distance from getting on the coaster to getting off the coaster (Most the time = 0)

Distance vs. Displacement What is the distance I walked? Distance = 6 meters What is my displacement from my starting point? Displacement = 2 meters

How are distance and displacement different? Distance is the length of the path between two points. Displacement is the difference between the starting point to the ending point.

Combining Displacements Displacement is an example of a vector A vector is a quantity that has magnitude and direction. The magnitude can be size, length or amount. Arrows on a graph or map are used to represent vectors

Vector A vector is any quantity that has both magnitude and direction. Magnitude & Direction Displacement 20 m, North

Combining Displacements The length of the arrow shows the magnitude of the vector.  Add displacements together using vector addition. Vector addition is the combining of vector magnitudes and directions. The vector sum of two or more vectors is called the resultant vector.

Combining Displacements in a Straight Line When two displacements, represented by two vectors, have the same direction, you can add their magnitudes. If two displacements are in opposite directions, the magnitudes subtract from each other. Most of the time displacement is expressed in a direction, like a compass. East = Right West = Left North = Up South = Down

Vector Addition Vector Addition If 2 similar vectors point in the SAME direction, add them. Example: A man walks 54.5 meters east, then another 30 meters east. Calculate his displacement relative to where he started? 54.5 m, E 30 m, E 84.5 m, E Notice that the SIZE of the arrow conveys MAGNITUDE and the way it was drawn conveys DIRECTION.

Vector Subtraction Vector Subtraction If 2 vectors are going in opposite directions, you subtract. Example A man walks 54.5 meters east, then 30 meters west. Calculate his displacement relative to where he started? 54.5 m, E 30 m, W 24.5 m, E

Combining Displacements in a Straight Line Examples

Combining Displacements in a Straight Line Activity:

11.1 Assessment Question #1 The straight line between the start and finish below represents: Distance Displacement Instantaneous Speed Speed Velocity  

11.1 Assessment Question #2 The curved path between the start and finish below represents: Distance Displacement Instantaneous Speed Speed Velocity  

11.1 Assessment Question #3 You leave the classroom and go to the bathroom, which is 10 meters away, and come back to your seat, what is you total distance? 0 meters 10 meters 20 meters Not enough information

11.1 Assessment Question #4 You leave the classroom and go to the bathroom, which is 10 meters away, and come back to your seat, what is you total displacement? 0 meters 10 meters 20 meters Not enough information

11.1 Assessment Question #5 What is the value of the resultant vector below? 2 units left 2 units right 6 units left 6 units right None of the above