Physics 218 Lecture 6

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Physics 218Lecture 6

• Dr. David Toback

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(No Transcript)
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Exam 1

• We will move the date of Exam 1 from Thursday
  Sept 26th, to Tuesday Oct 1st.
• Next week you need to do the reading for Chapter
  4 and Chapter 5. There will be quizzes on both.
• However, you will get recitation on Chapter 3 and
  turn in your Homework before the exam.

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Chapter 3

• Kinematics in Two Dimensions
• Vectors

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Projectile Motion

• This is the heart and culmination of what we have
  learned so far.
• You can rest assured there will be a problem like
  one in lecture today on the exam

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Firing up in the air at an angle
A ball is fired up in the air with velocity Vo
and angle Qo. Ignore air friction. The
acceleration due to gravity is g pointing
down. What is the final velocity here?
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Chase BEVO off a cliff

• Reveille chases BEVO off a cliff of height h. Two
  AM students observe that BEVO hits the ground a
  distance X from the base of the cliff.
• Assuming BEVO was moving horizontally at the top
  and ignoring air friction, how fast must he have
  been running?

h
y0
X
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Kick a football

• A football is kicked at angle Q0 with respect to
  the ground with speed V0. Calculate
• The maximum height
• The velocity at the maximum height
• The time of travel before the football hits the
  ground
• How far away it hits the ground
• What angle maximizes the distance traveled
• Assume the ball leaves the foot at ground level
  and ignore air resistance

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Winner Not my job award
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More Realistic Punt

• A football is kicked at angle Q0 with a velocity
  V0. The ball leaves the punters foot h meters
  above the ground.
• How far does it travel, in the X direction,
  before it hits the ground?

h
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Rescue Plane

• A rescue plane wants to drop supplies to isolated
  mountain climbers on a rocky ridge a height h
  below. If the plane is traveling horizontally
  with a speed of VO
• How far in advance of the recipients (horizontal
  distance) must the goods be dropped?

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Rescue Plane cont.

1. Suppose instead, that the plane releases the
   supplies a horizontal distance R in advance of
   the mountain climbers. What vertical velocity
   should they give the supplies so that they arrive
   precisely at the the climbers position.
2. What is the speed of the supplies as they hit the
   ground?

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Next Week

• Chapter 4 (NOT ON 1st EXAM) for Tuesday
• Dynamics
• Newtons Laws of Motion
• Chapter 5 Not on 1st Exam, for Thursday
• Finish HW3. Labs Rec/Web as usual
• No exam!!! It will be the following week.

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End of Lecture Notes
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Next Week

• Chapter 4 (NOT ON 1st EXAM)
• Dynamics
• Newtons Laws of Motion
• Finish HW3. Labs Rec/Web as usual
• Exam Thursday Here during regular time
• Bring a calculator and ruler
• Formula sheet will be provided (on the web
  already)
• Will cover
• Chapter 1 (1-6)
• Calculus 1
• Chapter 2 (1-7)
• Chapter 3 (1-8, 10)

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Example 3-8

• Derive a formula for the horizontal range, R, of
  a projectile in terms of its initial velocity (v0
  Q) before the projectile travels before
  returning to its original height