Ch. 2: Work and Energy

Question 1

Energy

Answer 1

The property of a system that enables it to do something or make something happen, including the capacity to do work. SI units for energy are joules (J) = kg*m2/s2

Question 2

Kinetic Energy

Answer 2

Energy associated with the movement of objects– depends on mass and speed squared (not velocity): K = ½ mv2

Question 3

Potential Energy

Answer 3

Energy stored within a system. Exists in gravitational, elastic, electrical. And chemical forms

Question 4

Gravitational potential energy

Answer 4

Related to the mass of an object and its height above a zero-point called a datum. (U = mgh)

Question 5

Elastic potential energy

Answer 5

Related to the spring constant (a measure of stiffness of a spring) and the degree of stretch or compression of a spring squared (U = ½ kx2)

Question 6

Electrical potential energy

Answer 6

Exists between charged particles

Question 7

Chemical potential energy

Answer 7

Stored in the bonds of compounds

Question 8

Mechanical energy

Answer 8

Sum of its kinetic and potential energies

Question 9

Conservative forces

Answer 9

Path independent and do not dissipate the mechanical energy of a system

• if only conservative forces are acting on an object, the total mechanical energy is conserved
• examples of conservative forces include gravity and electrostatic forces. elastic forces, such as those created by springs are nearly conserved

Question 10

Nonconservative forces

Answer 10

Path dependent and cause dissipation of mechanical energy from a system

• total energy is conserved, some mechanical energy is lost as thermal or chem energy
• examples of nonconservative forces include friction, air resistance, and viscous drag

Question 11

Work

Answer 11

Process by which energy is transferred from one system to another

• may be expressed as the dot product of force and displacement, or the product of force and distance travelled w the cosine of the angle between the two
• may be expressed as the area under a pressure volume (P-V) curve

Question 12

Power

Answer 12

Rate @ which work is done or energy is transferred. SI unit is watt (W)

Question 13

Work-Energy Theorem

Answer 13

When net work is done on or by a system, the system’s kinetic energy will change by the same amount. In more general application, the work done on or by a system can be transferred to other forms of energy as well

Question 14

Mechanical Advantage

Answer 14

Factor by which a simple machine multiplies the input force to accomplish work

Question 15

Simple machines

Answer 15

6 simple machines are inclined plane, wedge, wheel+axle, lever, pulley, and screw. Simple machines provide benefit of mechanical advantage

Question 16

Mechanical advantage

Answer 16

Makes it easier to accomplish a given amt of work bc the input force necessary to accomplish work is reduced; distance through which the reduced input force must be applied, however, is increased by the same factor

Question 17

Load

Answer 17

Output force of a simple machine, which acts over a given load distance to determine the work output of the simple machine.

Question 18

Effort

Answer 18

Input force of a simple machine which acts over a given effort distance to determine work input of the simple machine

Question 19

Efficiency

Answer 19

Ratio of the machine’s work output to work input when nonconservative forces are taken into account