SAU Conceptual Physics Dynamic Study Module CH.7
A weightlifter exerts an upward force on a 1000-N barbell and lifts the barbell 1 meter upward in 2 seconds. Approximately how much power does the weightlifter exert on the barbell during this time?
500 watts
Which of the following machines would be categorized as simple machines?
Levers & pulleys
Which of the following increases when a person runs a bag of groceries up the stairs rather than walking it up?
Power
Which of the following are major sources of energy?
Sun, wind, fossil fuels, and hydroelectric
When helping a friend move into a new home, you push a chair across the room. What do you know about the force of gravity applied to the chair?
The force of gravity applied to the chair does not change the energy of the system (the chair) and therefore does no work on the system.
When helping a friend move into a new home, you push a chair across the room. What do you know about the force that you exert on the chair?
The force you exert on the chair contributes to the overall change in kinetic energy of the system (the chair) with a positive amount and therefore does positive work on the system.
When helping a friend move into a new home, you push a chair across the room. What do you know about the force of friction applied to the chair by the floor?
The frictional force applied to the chair contributes to the overall change in kinetic energy of the system (the chair) with a negative amount and therefore does negative work on the system.
A block slides along a rough surface and comes to a stop. What can you conclude about the frictional force exerted on the block?
The frictional force does negative work on the block and decreases its kinetic energy.
When you lift a book upward off of a table, what is true about the work done on the book by the force of gravity?
The work done by the force of gravity is negative and proportional to the upward displacement of the book.
In which of these processes is the total energy of the system conserved?
Two balls of putty (the system) collide in midair and stick together.
A variety of forces are applied to an object such that the net force does positive work on that object. What can you conclude about the speed of the object?
When the total work done on the object is positive, the object's speed will increase.
__________ is required to change an object's energy.
Work
A simple machine that has a larger output force than input force must have
a larger input distance than output distance
kinetic energy is best defined as
energy of motion
Both __________ and __________ are required to change an object's energy level.
force, distance
The law of conservation of energy
is always true
Which of the following can create or destroy energy?
nothing
The most concentrated source of usable energy is that stored in
nuclear fuels
If Quantity X is conserved for a certain system and during a certain process, that means
quantity X for that system does not change in any way during that process
Potential energy is best defined as
stored energy
The change in the amount of work is equal to the change in kinetic energy is defined in
the work-energy theorem
It is impossible to achieve 100 percent efficiency in an engine due to
thermal energy
An apple falls from a tree. On the way to the ground, the apple's
total energy remains constant, potential energy decreases, and kinetic energy increases
Work done by a spring is work done by a
variable force
A man pushes against a wall with 200 N of force. The amount of work he does to the wall is
zero
