Presentation on theme: "Acceleration Section 6.1 in your textbook.. Thinking questions Describe the physical sensations (feelings) that you have when you experience these changes."— Presentation transcript:
Thinking questions Describe the physical sensations (feelings) that you have when you experience these changes in motion: Airplane taking off Car slowing down at a red light Driving along a circular ramp Why do you think that you feel these things?
Acceleration = change in velocity Object moves faster increase in magnitude (size) of velocity Object moves slower decrease in magnitude of velocity Object changes direction
What causes acceleration? Forces Anything that is pushing or pulling on the object No forces acting = no change in motion
Graphing Acceleration Acceleration is shown as a curve on a Position vs. Time graph The curve shows that velocity is changing The object has a larger change in position for each time interval
Acceleration on a Position vs. Time graph Describe the motion for each graph.
Acceleration on a Position vs. Time graph Increasing velocity in the positive direction Increasing velocity in the negative direction Decreasing velocity in the negative direction Decreasing velocity in the positive direction
These 3 graphs all show velocity that is increasing and acceleration that is constant.
Zero Acceleration Object is not changing velocity Position-Time graph: straight line increasing or decreasing Velocity-Time graph: flat line
Direction of Acceleration Slope of a Velocity vs. Time graph gives us information about the direction of acceleration Positive acceleration: slope of a VT graph is + Negative acceleration: slope of a VT graph is -
Positive Acceleration *does not always mean speeding up What happens right here?
Negative acceleration *does not always mean slowing down What happens right here?
What other information comes from a Velocity-Time graph? Displacement! Find the area under a Velocity vs. Time graph Area of a rectangle = length x width Area of a triangle = ½ base x height
Why does finding the area give us displacement? Think about the quantities represented by “length”, “width”, “base” & “height” on a VT graph. If velocity is constant, the area is a rectangle multiply time x velocity If velocity is changing uniformly, the area is a triangle multiply time x velocity & divide by 2 position changed a lot at the beginning, but a little at the end, so you’re actually finding the average change in position between the initial velocity & the final velocity