Bellwork

1
Bellwork

• Why dont you want your egg to bounce for the
  project?
• Because, it may hit the hard ground and crack /
  break.

2
Todays Agenda

• Follow-up on this weeks lab
• Momentum and Impulse notes
• Egg Drop Analysis
• Momentum and Impulse and the Egg Drop
• Sports Figures Video
• Next homework assignment

3
Work and Power Lab Follow-Up

• 1/10/14

4
Follow-up Questions (in your notes)

1. How can a large force result in relatively small
   power?
2. How can a small force result in relatively large
   power?

5
Follow-up Questions (in your notes)

• Combining Work and Power equations

6
Follow-up Questions (in your notes)

• Force and distance are directly proportional to
  power
• Time is indirectly proportional to power

7
Follow-up Answers(in your notes)

1. If the force is done over small distances and/or
   a long period of time
2. If the force is done over large distances and/ or
   a short period of time

8
Follow-up Answers with values

• Example F 5500 N d 0.015 m and t 3600 s
  is
• P 0.023 W
• Example F 5.5 N d 1500 m and t 0.36
  s is
• P 23,000 W

9
Momentum and Impulse Notes

• 1/10/14

10
Pre-Quiz(8 True/False Questions)

1. Impulses are normally smaller when bouncing takes
   place.
2. If a net force acts on an object, the object's
   momentum will change.
3. Momentum is defined as an object's mass times its
   velocity.
4. If the net external force acting on a system is
   zero, then the total momentum of the system is
   zero.

11
Pre-Quiz

1. Impulse is defined as the force exerted on an
   object times the time it lasts.
2. Automobile seatbelts are used to lengthen the
   time of impact in case of a collision.
3. When a baseball player follows through when
   hitting the ball, the contact time with the ball
   is longer.
4. The momentum of a large truck at rest is greater
   then the momentum of bee flying across the room.

12
Pre-Quiz Answers

1. Impulses are normally smaller when bouncing takes
   place. FALSE
2. If a net force acts on an object, the object's
   momentum will change. TRUE
3. Momentum is defined as an object's mass times its
   velocity. TRUE
4. If the net external force acting on a system is
   zero, then the total momentum of the system is
   zero. FALSE

13
Pre-Quiz Answers

1. Impulse is defined as the force exerted on an
   object times the time it lasts. TRUE
2. Automobile seatbelts are used to lengthen the
   time of impact in case of a collision. TRUE
3. When a baseball player follows through when
   hitting the ball, the contact time with the ball
   is longer. TRUE
4. The momentum of a large truck at rest is greater
   then the momentum of bee flying across the room.
   FALSE

14
Momentum and Impulse

• Momentum (vector) An object that is in motion
• Unit kg (m/s)
• Impulse (vector) The time and amount of force
  acting on an object
• Unit N s

15
Momentum and Impulse

• Impulses change the momentum of objects
• The longer the force acts on an object the
  greater the momentum change (following through on
  a swing)
• Extending impact times decreases the force (air
  bags and seat belts)

16
Momentum and Impulse

• In a collision, an object experiences a force for
  a given amount of time that results in its mass
  undergoing a change in velocity.
• Impulse change of momentum
• F t ? (m v)

17
Egg Drop Analysis

• Individual everyone needs to do the analysis
• Due Monday 1/27/14

18
Save an egg, crack a smile!
19
Oh no, Mr. Bill!
20
Momentum and Impulse and the Egg Drop Project

• F t ? (m v)
• You can not change the mass (m)
• You can not change the velocity (v)
• But you can try to change the time (t)
• So, what will this do to the force (F)?

21
Egg vs. Tile Floor

• F t Change of momentum

22
Egg vs. Grass

• F t Change of momentum

23
Egg Drop Project

• F t ? (m v)
• Your goal is to maximize the time!
• F t Change of momentum
• F t Change of momentum

24
Video
25
Homework

• IMPORTANT!!! If given the mass in kg you need to
  find the weight (Fg) of the object!
• Work and Power Problems
• Due Tues. 1/14/14