Wednesday 9/27 Please open quizizz
Graphing Acceleration VT Graphs
VELOCITY m/s VELOCITY TIME GRAPHS Moving in a positive direction, SPEEDING UP Constant speed NO ACCELERATION Moving in a positive direction, gaining speed at a SLOW rate TIME (sec) Moving in a NEGATIVE direction, DECELERATION slowing down
The slope of a velocity time graph is Slope = Δy = Change in velocity = Δx Change in time ACCELERATION The (instantaneous acceleration) of an object at a certain time is the slope of the velocity versus time graph at that time. It can be positive, negative, or zero.
Example 1: The velocity-time graph for a two-stage rocket is shown below. Use the graph and your understanding of slope calculations to determine the acceleration of the rocket during the listed time intervals 0 to 1 sec 1 to 4 sec 4 to 9 sec 9 to 12 sec + 40m/s 2 +20 m/s 2-20 m/s 2-20 m/s 2 accelerating upward Still accelerating Decelerating upward & moving Accelerating upward downward
Example 2 Describe the Motion Object is moving at a constant speed for the first 2 seconds in a positive direction, it then changes directions and is moving at a constant speed in a negative direction. Determine the Velocity Object is moving at a constant speed for the first 2 seconds there for there is no acceleration but a constant velocity in a positive direction, it then changes directions and is moving at a constant speed in a negative direction.
Example 3 Describe the Motion Determine the Velocity
Example 4: What distance does it travel in first the 20s? The distance covered is the area under the line. Area = ½ bh Distance = ½ (20s)(40m/s) Distance = 400 m
Example 4: b) What is the distance traveled during t=20s to t = 40s? Area = (b)(h) Distance = (20s)(40m/s) Distance = 800m c) What is the total distance? Distance = 400m + 800m = 1200m
Example 2: d) What is the average velocity during the first 40 seconds? Total Distance/Total Time 1200m/40sec = 30 m/s
Example 5:
Example 5:
Example 5:
Example 5:
You walk to the store at a CONSTANT SPEED. 0 m 10 m 10 8 6 4 2 You walk FASTER to the store at a CONSTANT SPEED. 0 m 10 m 10 8 6 4 2 4 6 8 Steeper line= faster 10 2 2 4 6 8 10
You RUN to the store but you get tired so you sit down to REST after you rest you walk to the store. 0 m 10 m 6 4 2 0-2 You leave the store and walk back home with a constant velocity. 0 m 10 m 6 4 2 0 2 4 6 8 10-2 2 4 6 8 10
v vs t graph Slope of line is acceleration Linear line represents uniform acceleration Horizontal line represents constant velocity, a=o Curved line represents changing acceleration Steeper slope represents greater acceleration Slope = Dv /Dt = acceleration Distance from detector cannot be indicated, only direction: away is positive and towards is negative
Position time graphs take away On Position vs Time graphs remember that - velocity is determined by slope of the line - distance is found by comparing the cart s position (the graph s y axis coordinate) at two times. Distance is a scalar quantity that does not depend on the direction of travel - average speed during an interval is the total distance traveled divided by the total time taken.
Review D v T Graphs Slope? What is happening? + or No motion, constant velocity, or acceleration? A B E F C D G H
Describe the motion of the dot. Constant positive velocity Don t worry about this one What does the position vs time graph look like? What does the velocity vs time graph look like?
Describe the motion of the dot. A negative constant velocity Don t worry about this one What does the position vs time graph look like? What does the velocity vs time graph look like?
Describe the motion of the dot. A positive velocity and a positive acceleration Don t worry about this one What does the position vs time graph look like? What does the velocity vs time graph look like?
Describe the motion of the dot. A positive velocity and negative acceleration Don t worry about this one What does the position vs time graph look like? What does the velocity vs time graph look like?
Describe the motion of the dot. A negative velocity and negative acceleration Don t worry about this one What does the position vs time graph look like? What does the velocity vs time graph look like?
Summary of a v/t Graph A B C
Compared to a d/t graph Constant speed Not moving Returning to starting position D i s t a n c e A B C
D v T Object is at rest at 0. It gradually increases speed (accelerates) forward from the start. Practice 3 +7 +7 V v T Object is at rest at 0. It gradually increases speed. (accelerates) forward from the start. meters meters meters/sec 0 sec 0 sec -7-7
Practice 4 Draw the V v T from the D v T D v T +7 +7 V v T meters meters/sec 0 sec 0 sec -7-7
Practice 4 Draw the V v T from the D v T D v T +7 +7 V v T meters meters/sec 0 sec 0 sec -7-7
Practice 5 Draw the D v T from the V v T D v T +7 +7 V v T meters meters/sec 0 sec 0 sec -7-7
Practice 5 Draw the D v T from the V v T D v T +7 +7 V v T meters meters/sec 0 sec 0 sec -7-7
D v T Object is at rest at 2m behind the origin. It stands still for 2 seconds. Then it moves forward at a 1 m/s for 5 seconds and then it stops for 3 seconds. The object the moves back towards the start at 2 m/s. Practice 6 +7 +7 V v T Object is at rest at 2m behind the origin. It stands still for 2 seconds. Then it moves forward at a 1 m/s for 5 seconds and then it stops for 3 seconds. The object the moves back towards the start at 2 m/s. meters meters/sec 0 sec 0 sec -7-7
D v T Object is at rest at 2m behind the origin. It stands still for 2 seconds. Then it moves forward at a 1 m/s for 5 seconds and then it stops for 3 seconds. The object then moves back towards the start at 2 m/s. +7 +7 V v T Object is at rest at 2m behind the origin. It stands still for 2 seconds. Then it moves forward at a 1 m/s for 5 seconds and then it stops for 3 seconds. The object then moves back towards the start at 2 m/s. meters meters/sec 0 sec 0 sec -7-7 Practice 6