Chapter 11: Motion Objectives: Identify frames of reference Distinguish between distance and displacement Interpret distance/time and speed/time graphs Calculate velocity and acceleration

11.1: Distance and Displacement ____________________________: – a system of objects that are not moving in respect to one another ____________________________: – Movement in relation to a frame of reference Question- (Throwing ball demonstration) 1. Describe the path of the object when the teacher stands still. 2. Describe the path of the object when the teacher moves forward. 3. How did the teacher view the path of the object? Why?

Distance: – the length of a path between two points – ___________________________________________________________________ ____________________________: – the direction and the length of a straight line between a starting point and end point – A _________________quantity (has magnitude and direction) unlike distance (only has magnitude) – Always ____________________________________________to distance because it is a straight line between two points, not always the actual path of the object’s motion. Question: (Walking around the room demonstration) 1.What is the teacher’s approximate distance that she traveled? 2.How does this compare to the displacement?

Vector Addition When the displacement of an object is in a straight line you can add the individual magnitudes. Ex: A car travels 2 km east, stops then travels 5 km east. What is the displacement? (Remember give magnitude and direction) Ex: A car travels 10km east, stops then travels 5km west. What is the displacement?

Displacement that is not in a Straight line When displacement is not in a straight line you must graph the x and y components of displacement then find the __________________ slope = ______________________ a² + b² = c² ; where “a” and “b” are the x and y components of the displacement and “c” is the slope (resultant vector or true displacement) Ex: A boy is going to school. He walks 1 block east, 1 block north, 2 blocks east, and 3 blocks north before he reaches school. What is the distance the boy traveled? What is the displacement?

11.2 speed and velocity ____________________: the ratio between the distance an object travels and the time it takes to travel that distance Expressed in m/s or km/hr (depending on the scale) Instantaneous speed- measured at a particular ___________________________ Average speed- total distance/total time __________________________ Ex: Calculate the average speed of a hiker who travels 6km in 0.75hr then in the next 0.25hr he travels 1km. How would the hiker’s instantaneous speed at the 20 min mark compare to his instantaneous speed at the 50 min mark? What possibly happened during this time?

Graphing speed Use a ________________________________________to show speed X axis = time (_____________________ variable) Y axis = distance (______________________ variable) Slope = _________________ How does the speed of the red line compare to the speed of the green line? What happened to the speed between points B and C?

Velocity The speed and ______________________ of an object’s motion (measured in m/s) A vector quantity including magnitude and direction If the _________________________________change then the velocity must change Ex: Compare the velocity of a car going around a racetrack at 120km/hr. Does the speed change? Does the velocity change? Why? Use vector addition to determine the resultant velocity. Ex. A boat is traveling 12km/hr west and the current of the water is 5km/hr west. What is the relative velocity of the boat? Ex. A boat is traveling 12km/hr west and the current of the water is 5km/hr east. What is the relative velocity of the boat?

Combining Velocities cont… Ex. A boat is traveling 12km/hr north and the water current is flowing 5km/hr east. What is the relative velocity of the boat? Hint: Use the pythagorean theorem

11.3 Acceleration The _____________________at which velocity changes May be a change in speed, a change in direction, or a change in both (+) change in speed = increase in speed = _______________________ (-) change in speed = decrease in speed = _______________________ Measured in ________________ Free Fall- acceleration due to gravity = _________________ Ex: A rock falls down a well. What is the rock’s speed at 1sec? At 2sec? What is the rock’s speed at 2sec? What is the rock’s acceleration?

Calculating Acceleration Acceleration = __change in velocity__ = total time Ex. Calculate the acceleration of a ball when it starts at rest then rolls down a ramp at 6m/s. Ex. A car traveling at 10m/s starts to decelerate. It comes to a stop after 20sec. What is it’s acceleration? Ex. An airplane travels down a runway for 4sec with an acceleration of 9.0m/s². What is the change in velocity during this time?

Graphing Acceleration Graph speed vs. time Speed = y axis (dependent variable) Time = x axis (independent variable) Slope = acceleration What happened between point O and A? What happened between point A and B? What happened between point B and C?

What happened during slope A? What happened during slope B? What happened during slope C?

Conclusions Draw a graph for each of the following scenarios 1. A car traveling at a low speed, stopping, then traveling at a high speed. 2. A car at a constant acceleration, then a constant speed, then a constant deceleration. 3. A car that is increasing in acceleration, not at a steady rate.