Momentum
Image: http://insidethecosmiccube.blogspot.com/2008/01/whats-story-mourning-glory.html
Vocabulary Sheets DueSept. 24
Monday
Sept. 8
Momentum
p = mv
p = momentum (kg·m/s)m = mass (kilograms, kg)v = velocity (meters/second, m/s)
Momentum = “amount of motion”
Example:A superhero of mass 75 kg is moving at 65 m/s.
Find the momentum of our man in tights.Find the velocity at which a freight train of mass 200,000 kg has the same momentum.
Impulse
I = FΔt
I = impulseF = force (Newtons, N)Δt = change in time (seconds, s)
pI
tFI
vmp
vmtFt
vmF
t
va
maF
Thanks Mr. Newton
Impulse is change in momentum
As Seen in Action Comics #13Superman stops a locomotive.
A 200,000kg train is moving at 15 m/s. After Superman flies into it, the train is moving at 0 m/s.
a) What impulse did Superman deliver to the train?
b) If Superman and the train were in contact for 2 seconds, what average force did he exert?
c) What was the average acceleration of the train during its contact with Superman?
Classwork
Page 193
Problems 2-6
Tuesday
Sept. 9
Energy Super Heroes
Projects due September 24
You must work at home on these. There’s not enough class time.
This week:1. Super power2. Name & origin story3. List of concepts your hero can demonstrate.
Energy Super Heroes
Presentations start on Sept. 24
Format:Slide show & speech VideoPoster presentationOthers?
Image: http://www.coverbrowser.com/covers/action-comics
Rubric: Super Hero ProjectWeek 2Objective Value
Hero is original 25
Super power relevant to our topic 25
Hero has a name and identity 25
List of concepts your hero can demonstrate (ie, what physics will you be showing?)
25
Superhero Energy Project
• Due Monday, September 15 by email or hard copy in class.
• From kinetic energy, potential energy, and conservation of energy, write 1 problem at minimum.
• From thermal energy, thermodynamics, and specific heat, write 1 problem at minimum.
• From momentum, impulse, and conservation of momentum, write 1 problem at minimum.
• Looking forward and due on Friday, Sept. 19: From any of the above topics, write 2 additional problems.
Friday
Sept. 12
How Fast
v2 = 2ghVelocity squared equals two times acceleration due to gravity times height
Note: How fast doesn’t care how heavy.
Impulse
I = FΔt
I = impulseF = force (Newtons, N)Δt = change in time (seconds, s)
pI
tFI
vmp
vmtFt
vmF
t
va
maF
Thanks Mr. Newton
Impulse is change in momentum
Terminal Velocity
The upper limit of how fast.
How fast? Skydiver with a semi-closed parachute: 195 km/h (120 mph)World record human freefall speed is 988 km/h (614 mph)
Source: http://en.wikipedia.org/wiki/Terminal_velocity
It happens when your weight is exactly balanced by an upward force called drag.
How long? About 15 seconds
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