Download Work Energy Power Assignment KEY

Work, Energy & Power Assignment KEY
Level 1
o Define all terms on pp. 218, 236, 262, 280 (omit ‘amplitude’), 301, 310
o Define gravitational potential energy
o Page 274: #5
o Page 327: #1, 2
Level 2
o Page 275-7: #16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 29, 36
o Page 270: #46, 47
Level 3
o Page 329: #21, 22
o A 225-g ball moves with a velocity of 30.0 cm/s to the right. This ball collides with a 125-g ball
moving in the same direction at a velocity of 10.0 cm/s. After the collision, the velocity of the
125-g ball is 24.0 cm/s to the right. A) What is the velocity of the 225-g ball after the collision?
B) Is this an elastic or inelastic collision? (Provide a mathematical reasoning for your answer)
o A 10.0-g object is moving with a velocity of 20.0 cm/s to the right when it collides with a
stationary 30.0-g object. After the collision, the 10.0-g object is moving left at a velocity of 6.00
cm/s. A) What is the velocity of the 30.0-g object after the collision? B) Is this an elastic or
inelastic collision? (Provide a mathematical reasoning for your answer)
Level 1
Kinetic energy – the energy of an object due to its motion
Potential energy – energy stored by an object
Mechanical energy – the sum of kinetic energy and potential energy of a system
Work – the transfer of mechanical energy
Joule – the unit of energy or work; equivalent to applying one Newton of force on an object over a distance of
one meter
Work-kinetic energy theorem – the relationship between the work done on an object and the resulting change in
kinetic energy
Work-energy theorem – the relationship between the work done on an object and the resulting change in any
form of energy of the object
Gravitational potential energy – the potential energy an object has because of its location in a gravitational field;
objects at higher altitudes have greater gravitational potential energy that objects at lower altitudes
Power – the rate at which work is done (or energy is transferred)
Efficiency – the ratio of useful energy (or work output) to the total energy (or work input); describes how well a
machine or device converts input energy or work into output energy or work
Conservative force – a force that does work on an object in such a way that the amount of work done is
independent of the path taken; work done by conservative forces is zero for motions in which the object returns
to the starting point (e.g. gravity)
Non-conservative force – a force that does work on an object in such a way that the amount of work done is
dependent of the path taken; work done by conservative forces is non-zero for motions in which the object
returns to the starting point (e.g. friction and air resistance)
Internal force – any force exerted on an object in the system due to another object in the system
External force – any force exerted by an object that is not part of the system on an object within the system
Open system – a system that can exchange both matter and energy with its surroundings
Closed system – a system that can exchange energy with its surroundings, but not with matter, i.e. objects
cannot enter or leave a closed system
Isolated system – a system that does not exchange either matter or energy with its surroundings, i.e. no external
forces enter the system
Elastic collision – a collision that conserves both momentum and kinetic energy
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Inelastic collision – a collision that conserves momentum but not kinetic energy
Conservation of momentum – the total momentum of two objects before a collision is the same as the total
momentum of the same two objects after they collide
Page 274
Page 327
Level 2
Page 275
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Page 270
46.
47.
Page 329
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Level 3
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