Physics ch 9 test
Identify two types of elastic potential energy.
1) A drawn bowstring 2) A compressed or stretched spring
Identify two types of chemical potential energy.
1) Energy in fuels, e.g. gasoline 2) Batteries
Identify the two types of mechanical energy.
1) Potential energy 2) Kinetic energy
Identify two types of gravitational potential energy.
1) Water in an elevated reservoir 2) Raised ram of a pile driver
Identify the two categories of work
1) Work done against another force 2) Work done to change the speed of an object
State the Law of Conservation of Energy—the 3 distinct parts.
1) energy cannot be created or destroyed 2) energy can be transformed from one form to another 3) the total amount of energy never changes
The equation for work is Work = force x distance. If the applied force is constant, how is the amount of work done related to the distance through which the force is applied?
Directly proportional
If a car is traveling along and the speed is reduced to half as fast as it was traveling, how does the car's kinetic energy change?
It has one-fourth as much kinetic energy
When we lift an object to an elevated position, what is the gravitational potential energy equal to?
It is equal to the work done against gravity lifting it.
A crane lifts a load of bricks that weighs 45000 N a distance = 15 m in a time = 45 s. If the time doubles, how is the power that is expended affected?
Power is cut in half
If there is some friction, it is the net force that causes a change in kinetic energy. How is the net force determined?
The net force equals the applied force minus the frictional force times the distance.
Describe what's happening when work is done on an object.
Work is done when a force acts on an object and the object moves in the direction of the force.
What is the "scientific" definition of the term work?
Work is the product of the force on an object and the distance through which the object is moved.
In a hydroelectric power plant gravitational potential energy is converted to
electrical energy
The property of an object or system that enables it to do work is
energy
The two common forces that we do "work" against are _____ and _____.
friction and gravity
When we apply the brakes in a car, the work is the _____ _____ supplied by the brakes multiplied by the _____ over which the friction force acts.
friction force, distance When we apply the brakes in a car, the work is the friction force supplied by the brakes multiplied by the distance over which the friction force acts.
The energy of motion is called _____ energy
kinetic
What is the equation for kinetic energy?
kinetic energy = 1⁄2 mass x (velocity)*2
According to the work-energy theorem, if there is NO friction at all—all of the work that is done appears as _____ _____.
kinetic energy. According to the work-energy theorem, if there is NO friction at all—all of the work that is done appears as kinetic energy.
The kinetic energy of an object depends on the _____ of the object as well as its _____.
mass, velocity
Power equals......
the amount of work done divided by the time interval during which the work was done.
Everywhere along the path of the pendulum bob, the sum of PE and KE is ___ _____. Because of the work done against _____, this energy will eventually be transformed into _____.
the same, friction, heat Everywhere along the path of the pendulum bob, the sum of PE and KE is the same. Because of the work done against friction, this energy will eventually be transformed into heat.
The kinetic energy of a moving object is equal to.....
the work required to bring it to its speed from rest, or the work the object can do while being brought to rest.
The upward force required while moving at a constant velocity is equal to the....
weight of the object
The work-energy theorem states that whenever _____ is done, _____ _____ changes. Work = Work equals _____ __ _____ _____.
work, kinetic energy The work-energy theorem states that whenever work is done, kinetic energy changes. Work = ^ KE Work equal change in kinetic energy
If a force causes an object to move at a constant speed, what is the net force equal to? What is the change in kinetic energy equal to?
zero <net force and net work equal zero> ^KE = 0