lecture 17 work and kinetic energy
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Lecture 17: Work and Kinetic Energy Objectives 1. Relate the work done by a constant force to the change in kinetic energy of a system. 2. Apply the work-kinetic energy theorem to systems with constant forces.
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If an object is moving, then it is capable of doing work.
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Work is related to the change in speed of an object.
If an object is moving, then it is capable of doing work. It has energy of motion, or kinetic energy (KE).
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Kinetic energy is related to the motion of an object.
Energy is a property of objects, transferable among them via fundamental interactions, which can be converted in form but not created or destroyed.
If an object is moving, then it is capable of doing work. It has energy of motion, or kinetic energy (KE).
An infrared camera reveals the heated tire track on the floor. (image: Conceptual Physics, JP Hewitt) 5
Kinetic energy is related to the motion of an object.
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Work-energy theorem: when work is done, energy changes
http://zonalandeducation.com/mstm/physics/mechanics/energy/work/work.html
Kinetic energy carries no information about the direction of motion.
Valid only to inertial frame of reference.
If an object is moving, then it is capable of doing work.
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Work is related to the change in speed of an object.
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Work-energy theorem: when work is done, energy changes
Work is a transfer of energy!
http://zonalandeducation.com/mstm/physics/mechanics/energy/work/work.html
Golfer does work on the club
Club does work on the
ballEnergy in the golfer
Energy in the club
Energy in the ball
Sample Problem: (Sled again) A 14700N sled is being pulled by a tractor with the total work done on the sled as 10KJ. If the sled has an initial speed v1 of 2.0m/s, what is the speed of the sled after it moves 20m?
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Solve for h and substitute the given values:
Same work-kinetic energy equations will be used to solve for h:
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A box (mass 2.00 kg) slides along a frictionless irregular road. It starts from rest at point A 2.00 m above the ground and reached point B at 6.26m/s.
1. What is the total work done when it reaches point B?
2.00 m
A
B
Seatwork
Seatwork
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2. Which iceboat crosses the finish line with greater kinetic energy?
3. Which iceboat crosses the finish line first?
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A box (mass 2.00 kg) slides along a frictionless irregular road. It starts from rest at point A 2.00 m above the ground and reached point B at 6.26m/s.
1. What is the total work done when it reaches point B? W = (1/2)(2.00kg)(6.26m/s)2 – 0 = 39.2 J
2.00 m
A
B
Seatwork