Monday 10-15 Finish School Buses Intro to momentum.
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Transcript of Monday 10-15 Finish School Buses Intro to momentum.
Monday 10-15
Finish School Buses
Intro to momentum
Today
• Seatbelt paper – (Rubric handed out on Tuesday)
• Pages in yellow workbook to be completed
• Momentum– In terms of collisions– In terms of games– In terms of people
Yellow Book pages
• 2 and 3• 14• 15-22 all parts (might need to go back and
complete• 23-25 (only predictions and observations)• 27 only the scroll• 29(entire page), 30 (only chart)• 35-37 questions• 45 (entire page)
Homework
• Practice Problems p 363 (1,2)
• Problems on page 366 (1 through 6)
• 2nd law problems on pg 367 (1-3)
Would you support a law that requires all school buses to have
seat-belts?
RubricSeat belt paper (50 points) Friday
• Up to nine points each for:– At least 3 worthwhile reasons for seatbelts– At least 3 worthwhile reasons against belts– Connection between each law to seatbelts
• Up to six points each for:– Clear statement of position on seatbelts– How well the project written– Condition of project
• Up to 4 points for:– references from outside articles or other sources
Which would you rather get hit by?
• 1 bowling ball? • 1 marble ?
Momentum
• A quantity of motion
• Found by multiplying the mass of an object by its velocity
• Momentum = mass x velocity
Units
• Momentum = kg m/s
• Not the same as Forces (N = kg m/s2)
• Momentum is not a force
Momentum equation
P = m v
P
M V
2nd law and velocity equation can also be drawn in a similar fashion
Fnet = m a D = v t
M A t
If the object moves, and has mass , it has momentum
Objects gain and lose momentum due to forces being applied
To catch a tennis ball
• Your hand must apply force to the ball to make it stop moving
The change on momentum
• Related to the change in velocity
• Mass is usually kept constant
• Related to the amount of force applied
• Related to the time is takes to achieve the change
To make something stop (Change of momentum constant)Apply a lot of force in a short period of time
or
Apply a small force over a longer time
The purpose of most safety features in a car is to lengthen the
time of the accident• Air bags
Seat belts
Padding on dashboard, seats and steering wheel
Crumple zones
• It takes time for the parts of the car in the crumple zone to be crushed, less force applied to the passenger section
Any other means to protect the passengers during a collision?
Other examples of change in momentum
• Catching a Foul Ball • Being hit by a foul ball
Momentum is conserved
• Conserved means that the momentum can be transferred from one object to another, but not lost to the system
Newton’s Cradle