• How long did it take for the sound to reach you? • How long did it take the bee to reach the elephant? • How fast was the bee flying? • If the bee returns promptly to his starting position maintaining the same speed, what was his average velocity?
Interpreting Velocity Graphically • The instantaneous velocity is the velocity of an object at some instant or at a specific point in the object’s path The instantaneous velocity at a given time can be determined by measuring the slope of the line that is tangent to that point on the position-versus-time graph
Check Point Do you calculate instantaneous velocity the same way you calculate average velocity? What is the difference?
9/17 • HW- Book p. 49 1-5. Graphs must be done by Monday! • Describe the motion of the objects in the following graph
Objectives • Describe motion in terms of changing velocity. • Compare graphical representations of accelerated and non-accelerated motions. • Apply kinematic equations to calculate distance, time, or velocity under conditions of constant acceleration.
• Acceleration is the rate at which velocity changes over time. average acceleration = • An object accelerates if its speed, direction, or both change. • Acceleration has direction and magnitude. Thus, acceleration is a vector quantity a avg = = SI Unit: m/s 2
Data and Graphs from Yesterday • Now take the data and for each trial, convert each data set into velocity (y axis) and time (t on x axis) • Make sure you clearly label the trials and the type of motion that was occurring • Look at the lines that were produced on each graph and describe the motion at each line segment (you may neatly write this on the graph). Here you are making mental comparisons between the first graphs which show P-T and these graphs which show V-T • Calculate the slope and area under each line segment for Each Trial (you may neatly write this on the graph)
Finding Displacement During Constant Acceleration • Remember that velocity is displacement (∆ x) over time so with some rearranging, we can get a new equation from acceleration that allows us to find out how far and object traveled given it’s velocities and the time of the motion. t v v x i f ) ( 2 1
What if? • A plane starting at rest at one end of the runway undergoes uniform acceleration of 4.8 m/s/s for 15 s before takeoff. • What is the speed at takeoff? • How long must the runway be for the plane to takeoff?
Finding Velocity with Constant Acceleration Finding Displacement with Constant Acceleration All we are doing is rearranging the first two equations! at v v i f 2 2 1 at t v x i
• At the Dixie Stampede in Pigeon Forge, the pig Abraham Linksausage ran around a circular path. Suppose Abe can run at a max speed of 2 feet/sec. If he started from rest and underwent constant acceleration with a magnitude of 0.5m/s/s, what distance did he have to run to reach his max speed?
You've reached the end of your free preview.
Want to read all 71 pages?