Chapter 10 - Energy and Work

What are the two primary energy-transfer processes?

- Work - Heat

For an isolated system, we must set W = to what?

0

Which angle of force applied gives the maximum energy transfer into the system

0 degrees

On an energy diagram of a spring, what sets the total energy line? Can this be changed?

1. Compression or extension of the spring 2. Yes

On an energy diagram, the total energy line is always __________ because the sum of the kinetic and potential energy is the __________ at every point.

1. Horizontal 2. Same

Hot objects have (more/less) thermal energy than cold ones because why?

1. More 2. The molecules move more

On an energy diagram, if the total energy line crosses the potential energy curve at two positions, the object will do what? The mid-point between these two points will be the object's what?

1. Oscillate between these two positions 2. The maximum speed

On an energy diagram of a spring, consider the spring being pulled back and released. What does the middle point of the parabola represent? What type of energy is present?

1. The point of maximum speed 2. Only kinetic energy

On an energy diagram of a spring, the potential energy curve is determined by what? Can it be changed?

1. The spring constant 2. No

The before-and-after work-energy equation states that a system's final energy, including any change to the system's __________ __________, equals its __________ __________ plus any energy added to the system as __________.

1. Thermal energy 2. Initial energy 3. Work

On an energy diagram of a spring, consider the spring being pulled back and released. What do the end points of the parabola represent? What type of energy is present?

1. When the spring is entirely stretched or compressed 2. Only potential energy

Which angle of force applied gives the maximum energy transfer out of the system?

180 degrees

Which angle of force applied transfers no energy?

90 degrees

The equation for rotational kinetic energy is not what?

A new form of energy

Heat transfers energy from the environment to the system (or vice versa) because of what?

A temperature difference

On an energy diagram, a position where the total energy line crosses the potential energy curve signifies what?

A turning point

The joule is the unit for which forms of energy?

All of them

What is an exchange of energy between system and environment?

An energy transfer

If one form of energy in a system decreases, it must do what?

Appear in equal amount in another form

Potential energy has the potential to do what?

Be converted into other types of energy

Only __________ in potential energy are significant.

Changes

Energy stored in the bonds of molecules that can be released at a later time when the bonds are rearranged during chemical reactions.

Chemical energy

The total energy of an isolated system remains what?

Constant

Energy is neither created nor __________.

Destroyed

If the object undergoes no __________ while the force acts, no work is done.

Displacement

If the part of the object on which the force acts undergoes no __________, no work is done.

Displacement

Energy stored when a spring or other elastic object is stretched.

Elastic potential energy

Only (internal/external) forces can change the amount of energy within a system.

External

(True/False) The external force the ramp exerts on an object sliding down it is included in when considering the situation as an isolated system.

False

If force is being applied at an angle, and the force is broken down into force perpendicular and force parallel, which is the only force that does work on the object?

Force parallel

An increase in thermal energy is a general feature for any system in which there is what?

Friction between sliding objects

Stored energy associated with an object's height off the ground.

Gravitational potential energy

In the object + earth system, the higher an object is lifted, the (greater/less) the gravitational potential energy.

Greater

The (greater/smaller) the force, the more work that is done.

Greater

The kinetic energy of a rolling object is always __________ than that of a nonrotating object moving at the same speed.

Greater

What is the nonmechanical transfer of energy?

Heat

A force does the greatest possible amount of work on an object when it points where?

In the same direction as the displacement

In the basic energy model, the arrows between kinetic, potential, and chemical energy and thermal energy are shown as one-way because why?

It is difficult to transform energy back from thermal

In the basic energy model, the arrows between kinetic, potential, and chemical energy are shown as two-way because why?

It is easy to transform energy back and forth between these forms

When an object moves at a constant speed, what happens to the kinetic energy?

It stays the same

All moving objects have __________ energy.

Kinetic

On an energy diagram (kinetic energy vs gravitational potential energy), consider a ball moving upward. When the ball is at a height of y1, the distance from the potential energy curve to the total energy line is which of the ball's energies at that position?

Kinetic energy

The energy of motion.

Kinetic energy

When an object is heated, its atoms move around quickly, raising their what?

Kinetic energy

The (smaller/larger) the displacement, the more work that is done.

Larger

The heavier an object is and the faster it moves, the (more/less) kinetic energy it has.

More

Energy is transferred as work only when the system __________ while the force acts.

Moves

Energy that comes from the forces that hold together the nuclei of atoms.

Nuclear energy

A force __________ to the displacement does no work.

Perpendicular

On an energy diagram (kinetic energy vs gravitational potential energy), consider a ball moving upward. When the ball is at a height of y1, the distance from the axis to the potential energy curve is which of the ball's energies at that position?

Potential energy

When an object is heated, the atoms are moved further from their equilibrium positions, which raises their what?

Potential energy

What is the rate at which energy is transformed?

Power

Work transfers energy to or from a system by doing what?

Pushing or pulling on it

What is the term for kinetic energy of an object in rotational motion?

Rotational kinetic energy

Work is a (vector/scalar) quantity.

Scalar

On an energy diagram, any local minimum on the potential energy curve is a point of what?

Stable equilibrium

What is an equilibrium for which a small disturbance only causes a small oscillation?

Stable equilibrium

When two or more objects in a system interact, it is sometimes possible to do what with the energy?

Store it

Force and distance are always positive, so what determines the sign of work?

The angle between the force and the displacement

Gravitational potential energy depends only on what?

The height of the object above the reference level y = 0

Gravitational potential energy does not depend on what?

The path the object took to get to its position.

What is the total kinetic energy of a rolling object that is undergoing both rotational and translational motion?

The sum of its kinetic energies.

Internal forces cannot change what?

The system's total energy

On an energy diagram, the object represented cannot be in a position where the potential energy curve is above what?

The total energy line

The sum of the microscopic kinetic and potential energies of all molecules in an object.

Thermal energy

Every system in nature has associated with it a quantity we call its what?

Total energy

What is the sum of the different kinds of energies present in a system?

Total energy

Energy of one kind can be ____________ into energy of another kind.

Transformed

What is the term for the kinetic energy of an object moving along a line?

Translational kinetic energy

On an energy diagram, an local maximum in the potential energy curve is a point of what?

Unstable equilibrium

What is an equilibrium position for which any small disturbance drives the particle away from equilibrium?

Unstable equilibrium

Energy transformations are changes (within/outside of) the system from one form to another.

Within

In an isolated system, what is removed from the before-and-after work-energy equation?

Work

What is the mechanical transfer of energy?

Work

Transferred energy changes the system's energy by exactly the amount of what?

Work that was done