Engineering Physics (Option 3)

Question 1

Adiabatic

Answer 1

A reaction is described as adiabatic if no heat passes to or from the gas. When no heat enters or leaves, the total work done on the system must be equal to the negative change of internal energy.

Question 2

Angular Acceleration

Answer 2

The rate of change of an object’s angular velocity. Angular acceleration is a vector quantity.

Question 3

Angular Displacement

Answer 3

The angle in radians that a rotating object has travelled through.

Question 4

Angular Impulse

Answer 4

Equal to the product of the resultant torque acting, and the time period over which it acts. It equals the change of angular momentum that occurs in that time.

Question 5

Angular Momentum

Answer 5

The product of an object’s moment of inertia and angular velocity.

Question 6

Angular Speed

Answer 6

The rate of change of an object’s angular distance. Angular speed is a scalar quantity.

Question 7

Angular Velocity

Answer 7

The rate of change of an object’s angular displacement. Angular velocity is a vector quantity.

Question 8

Brake Power

Answer 8

The power present at the output shaft of an engine. It is equal to the indicated power minus any power lost to friction.

Question 9

Coefficient of Performance

Answer 9

A measure of how good a device is at converting work into a heat transfer. Note that this value can sometimes be greater than one.

Question 10

Conservation of Angular Momentum

Answer 10

The angular momentum before an event is equal to the angular momentum after an event, as long as no external torque acts.

Question 11

Constant Volume Reaction

Answer 11

When the volume doesn’t change in a reaction, the boundary cannot move and so no work can be done. This means that for constant volume reactions, the heat supplied must be equal to the change of internal energy.

Question 12

First Law of Thermodynamics

Answer 12

A form of the conservation of energy. It states that the total energy supplied or removed from a system is equal to the sum of the change in internal energy and the work done on it.

Question 13

Flywheel

Answer 13

Devices that accumulate and store energy. They can also be used to even out fluctuations in an object’s rotational speed.

Question 14

Four-Stroke Engine

Answer 14

A type of engine cycle in which fuel is burned once every four strokes. The four stages are induction, compression, expansion, and exhaustion.

Question 15

Indicated Power

Answer 15

The power developed within the cylinders of an engine.

Question 16

Indicator Diagrams

Answer 16

The name given to the p-V diagram for an engine cycle. They give an indication of an engine’s performance.

Question 17

Isothermal

Answer 17

A reaction is described as being isothermal if it occurs at a constant temperature. When temperature doesn’t change, the internal energy must remain constant.

Question 18

Isotherms

Answer 18

Lines of constant temperature, drawn onto p-V diagrams. Isotherms of higher temperatures are found further away from the origin.

Question 19

Mechanical Efficiency

Answer 19

The ratio of brake or output power over the indicated power.

Question 20

Moment of Inertia

Answer 20

The product of the mass and the square of the radius (from the axis of rotation) for a rotating body. For extended objects, the moments of inertia for each element can be summed.

Question 21

Overall Efficiency

Answer 21

The ratio of brake or output power over the total power inputted.

Question 22

Reversed Heat Engine

Answer 22

A form of heat engine in which work is inputted. Energy passes from a cold reservoir into a hot reservoir.

Question 23

Rotational Kinetic Energy

Answer 23

Equal to half the product of the moment of inertia and the square of the angular velocity of a rotating body. For extended objects, the rotational kinetic energies for each element can be summed.

Question 24

Second Law of Thermodynamics

Answer 24

A law that all engines must obey, and which states that any process that converts heat into work, cannot have an efficiency that approaches 100%.

Question 25

Sink

Answer 25

The sink of an engine is where some energy from the engine is rejected. It is at a lower temperature than the source. If the sink were to be at absolute zero, the engine would have 100% efficiency.

Question 26

Source

Answer 26

The source of an engine provides heat to the engine. It is at a higher temperature than the sink. In general, the higher the temperature of the source, the higher the efficiency.

Question 27

Theoretical Diesel Engine

Answer 27

An engine cycle consisting of adiabatic compression, the supply of heat at constant pressure, adiabatic expansion, and then finally constant volume energy rejection.

Question 28

Theoretical Otto Cycle

Answer 28

A cycle involving air undergoing adiabatic compression, heat being supplied under constant volume, adiabatic expansion, and then finally constant volume energy rejection.

Question 29

Thermal Efficiency

Answer 29

The ratio of indicated power over the power inputted.

Question 30

Torque

Answer 30

A force that produces rotation. It is equal to the product of force and rotational radius.