Transcript Work, Energy and Conservation of Energy

Physics Spring 2015
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Go Over Friction Quest
◦ Take the Friction Quest if missing yesterday
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Second Semester Review Assignment
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Notes: Work
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Review Mid-Semester Review
◦ Collect Review
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Notes: Work and Power
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Practice: Work and Power
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HW: Complete the Work and Power
Assignment
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Which of these would you classify as doing
work?
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Lifting weights
Climbing stairs
Moving a couch
Trying to push a car that is stuck
Carrying you backpack around school
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Work is the application of any force over a
distance.
The equation for work is…
Work = Force x distance
◦ If there is an applied force, but no movement is
working being done?
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Which requires more work, to move 10 2N
books 10m one at a time, or move all of the
books at once?
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How did we measure power in the circuits
unit?
What did we say that the electricity company
sells us actually?
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Power is still the rate of energy used per time
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In this unit:
◦ Power = Work (J) / time (sec)
◦ Units: Watts
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A person expends 500J of energy while
climbing a flight of stairs. If it takes this
person 15 seconds to climb this flight, how
much power did this person use?
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If a car uses 100,000J of energy over the
course of a 120 second drive. What is the
power used?
If one horse can expend 30 Watts of power,
how much horsepower was this car using?
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Review Work Assignment
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Horsepower Lab
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Burning Calories Analysis and Conclusion of
lab
HW: Complete Lab if not done in class
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The energy of position or height
This tells us how much work an object could
do.
GPE = mass * acceleration of gravity * height
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The energy of movement
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The amount of energy a moving object has.
KE = ½ mass * velocity2
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Energy can never be created nor destroyed it
just changes forms, from GPE to KE.
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As GPE decreases, the amount of KE increases.
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As KE decreases, the amount of GPE decreases.
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Horsepower Lab
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PE v. KE note review
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Practice Problems: PE v. KE
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Energy Skate Park
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HW: PE v. KE assignment
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What is the kinetic energy of a fastball
(.149kg) traveling at 26.6 m/s?
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How much potential energy does a ball have
that is held motionless at a distance of 100m
if the ball has a mass of 2kg.
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Energy Note Check
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Work and Energy Practice
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LOCOE Exit Slip
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HW: None
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Go Over exit slip procedures
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Notes: Conservation of energy
◦ Resubmit Exit slip from yesterday
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Bowling Ball Demo
◦ Chromebook research
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Bowling Ball Explanation Activity
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Energy is NEVER created or destroyed. It is
only transformed into a different form of
energy.
When an object is at rest above the ground
contains 100% potential energy.
An object moving very close to the ground
(height = 0m) it contains 100% KE
100% GPE
100% KE
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If a basketball is dropped from a height of 1m, how
fast will it be moving when it hits the ground? The
basketball has a mass of .3kg.
GPE (before dropped) = mgh = .3kg * 10m/s2 * 1m
3J
GPE at top = KE at bottom (Conservation of Energy)
KE (at bottom) = ½mv2 => ½ *.3kg * v2
v = .39 m/s
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Review Bowling Ball Lab
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Rollercoaster Problem
◦ Conservation of Energy
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Before tomorrow Quiz on LOCOE
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HW: None, unless you need practice
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Finish Quiz/Rollercoaster Problem
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Work and finish Spring Energy Lab
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Happy Prom Weekend!!
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HW: None
Let me see you all on Monday!