1 / 14

Classical Mechanics Lecture 3

Classical Mechanics Lecture 3. Today ’ s Concepts: a) Relative motion b) Centripetal acceleration. Prelecture 3, Question 1. CheckPoint.

ina
Download Presentation

Classical Mechanics Lecture 3

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. Classical Mechanics Lecture 3 Today’s Concepts: a) Relative motion b) Centripetal acceleration

  2. Prelecture 3, Question 1

  3. CheckPoint A girl stands on a moving sidewalk that moves to the right at 2 m/srelative to the ground. A dog runs toward the girl in the opposite direction along the sidewalk at a speed of 8 m/s relative to the sidewalk. What is the speed of the dog relative to the ground? vdog,belt= 8 m/s vbelt,ground= 2 m/s A)6 m/sB)8 m/sC)10 m/s

  4. What is the speed of the dog relative to the ground? vdog,belt= 8 m/s +x vbelt,ground= 2 m/s vdog, ground = vdog, belt + vbelt, ground = (-8 m/s) + (2 m/s) = -6 m/s A)6 m/sB)8 m/sC)10 m/s

  5. CheckPoint A girl stands on a moving sidewalk that moves to the right at 2 m/s relative to the ground. A dog runs toward the girl in the opposite direction along the sidewalk at a speed of 8 m/s relative to the sidewalk. What is the speed of the dog relative to the girl? vdog,belt= 8 m/s vbelt,ground= 2 m/s A)6 m/sB)8 m/sC)10 m/s About 55% of you got this right – lets try it again.

  6. Tractor Demo (moving cardboard) Which direction should I point the toy bulldozer to get it across the cardboard fastest? A) To the left B) Straight across C) To the right A B C

  7. Clicker Question A man starts to walk along the dotted line painted on a moving sidewalk toward a fire hydrant that is directly across from him. The width of the walkway is 4 m, and it is moving at 2 m/s relative to the fire-hydrant. If his walking speed is 1 m/s, how far away will he be from the hydrant when he reaches the other side? 1 m/s • 2 m • 4 m • 6 m • 8 m Moving sidewalk 2 m/s 4 m

  8. If the sidewalk wasn’t moving: 1 m/s Time to get across: Dt = distance / speed = 4m / 1m/s = 4 s 4 m

  9. Just the sidewalk: 2 m/s 4 m

  10. Combination of motions: 1 m/s 4 m 2 m/s

  11. 1 m/s D 2 m/s 4 m D = (speed of sidewalk) ∙ (time to get across) = (2 m/s) ∙ (4 s) = 8 m

  12. Three swimmers can swim equally fast relative to the water. They have a race to see who can swim across a river in the least time. Relative to the water, Beth swims perpendicular to the flow, Ann swims upstream at 30 degrees, and Carly swims downstream at 30 degrees. Who gets across the river first? A) AnnB) BethC) Carly Clicker Question y x Beth Ann Carly

  13. Look at just water & swimmers y x Time to get across=D / Vy B A C D 30o 30o Vy,Beth = Vo Vy,Ann = Vocos(30o) Vy,Carly = Vocos(30o)

  14. Clicker Question Three swimmers can swim equally fast relative to the water. They have a race to see who can swim across a river in the least time. Relative to the water, Beth swims perpendicular to the flow, Ann swims upstream at 30 degrees, and Carly swims downstream at 30 degrees. Who gets across the river second? A) AnnB) Carly C) Both same y x Ann Carly

More Related