1 / 29

Physics I 95.141 LECTURE 5 9/20/10

Physics I 95.141 LECTURE 5 9/20/10. Outline . Review of Lecture 4 Projectile Motion What do we know? Units Kinematic equations Freely falling objects Vectors Kinematics + Vectors = Vector Kinematics Relative motion. Exam Prep Problem.

muniya
Download Presentation

Physics I 95.141 LECTURE 5 9/20/10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics I95.141LECTURE 59/20/10

  2. Outline • Review of Lecture 4 • Projectile Motion • What do we know? • Units • Kinematic equations • Freely falling objects • Vectors • Kinematics + Vectors = Vector Kinematics • Relative motion

  3. Exam Prep Problem • An object starts from rest at the origin. If the acceleration of the object is given by: • A) (10pts) Give the velocity and displacement of the object, as a function of time. • B) (5pts) What is the object’s velocity and speed at 10s? • C) (5 pts) What is the object’s displacement at 10s? • D) (5 pts) What is the average velocity of the object for the first 10 seconds of motion?

  4. Exam Prep Problem • An object starts from rest at the origin. If the acceleration of the object is given by: • A) (10pts) Give the velocity and displacement of the object, as a function of time.

  5. Exam Prep Problem • An object starts from rest at the origin. If the acceleration of the object is given by: • B) (5pts) What is the object’s velocity and speed at 10s?

  6. Exam Prep Problem • An object starts from rest at the origin. If the acceleration of the object is given by: • C) (5 pts) What is the object’s displacement at 10s?

  7. Exam Prep Problem • An object starts from rest at the origin. If the acceleration of the object is given by: • D) (5 pts) What is the average velocity of the object for the first 10 seconds of motion?

  8. Projectile Motion (displacement) • Projectile motion is a special case of motion with constant acceleration: the acceleration due to gravity • Here, the acceleration is in only one direction! • The equations of motion become:

  9. Projectile Motion (Equations Of Motion)

  10. Projectile Motion (velocity) • We can always find the expression for velocity by differentiating the expression for displacement with respect to time.

  11. Projectile Motion (acceleration) • We can always find the expression for acceleration by differentiating the expression for velocity with respect to time.

  12. Projectile Motion • Problem Solving Strategy • Draw a diagram, choose coordinate system • Split into x, y components of motion • Think about what problem is actually asking! • List unknowns and knowns • Apply relevant equations and solve

  13. Example • Say I hit a golf ball with initial velocity vo at an angle of θº. • Find equations of motion • Find ball height as a function of lateral position (y(x)) • Find the Range of the ball (assuming ground is flat) • The time of flight

  14. Example Problem y x Vyo Vxo • Say I hit a golf ball with initial velocity vo at an angle of θº. • A) Find equations of motion • Draw diagram and choose coordinate system • Fill in knowns

  15. Example Problem • Say I hit a golf ball with initial velocity vo at an angle of θº. • B) Find y(x) • Write out equations • Solve for y(x)

  16. Example Problem y x • Say I hit a golf ball with initial velocity vo at an angle of θº. • C) Find Range (distance ball travels before hitting ground) • What does this mean in numbers?

  17. Example Problem (Extra) y x • Say I hit a golf ball with initial velocity vo at an angle of θº. • C+) Find the θ for maximum Range • What does this mean in numbers?

  18. Example Problem y x • Say I hit a golf ball with initial velocity vo at an angle of θº. • D) Find time of flight (time ball travels before hitting ground) • What does this mean in numbers?

  19. Projectile Motion • For a typical projectile motion problem, we can think about the object motion in component form.

  20. Example Problem • A punter, on average, can give the football an initial velocity of 27m/s. The Cowboy’s new $1.2 Billion stadium has a scoreboard 90ft (27.5m) off the ground. What is the minimum angle required for an average punt to hit the scoreboard? • Find initial y-velocity required to hit scoreboard

  21. Example Problem • A punter, on average, can give the football an initial velocity of 30m/s. The Cowboy’s new $1.2 Billion stadium has a scoreboard 90ft (27.5m) off the ground. What is the minimum angle required for an average punt to hit the scoreboard? • What is angle?

  22. The Speed Bus • OK, so we know: • DRAW DIAGRAM!! • Determine knowns • Pick Equations

  23. Speed Bus with Magic Launch • OK, so we know new • DRAW DIAGRAM!! • Determine knowns • Pick Equations

  24. Does it make it?

  25. Example (Rescue Helicopter) • Helicopter wants to drop supplies on mountain top 200m below. Helicopter flying horizontally at 70m/s • A) How far in advance (horizontal distance) should the package be dropped? • Draw diagram, choose coordinate system • Knowns and unknowns

  26. Helicopter, Part (a) • Divide equations into x and y

  27. Example (Rescue Helicopter) • Helicopter wants to drop supplies on mountain top 200m below, 400m in advance. Helicopter flying horizontally at 70m/s • B) What vertical velocity should the package be given? • Draw diagram, choose coordinate system, time interval • Write out equations

  28. Helicopter, Part (b) • Divide equations into x and y

  29. Now We Know • Projectile Motion • Motion in component form • Problem solving approach

More Related