Rotational Motion & Astrophysics

Question 1

What is a Circumference?

Answer 1

The Length of the Perimeter of a Circle

Question 2

What is an Arc?

Answer 2

The length of a section of the Circumference of a Circle

Question 3

What is a Diameter?

Answer 3

The Length of the Line connecting opposite sides of a Circle through its center

Question 4

What is a Radius?

Answer 4

The Length of the Line connecting the Edge of a Circle to its center

Question 5

What is a Tangent?

Answer 5

A Line at a right angle to the Radius that ‘touches’ the edge of a Circle.

Question 6

How many radians for 1 complete circle?

Answer 6

2π radians

Question 7

What is meant by “Angular displacement”?

Answer 7

The change in angular position between two points.

Question 8

What is meant by “Angular Velocity”?

Answer 8

The rate of change of Angular Displacement

Question 9

What is meant by “Periodic time”?

Answer 9

Time taken for 1 complete revolution

Question 10

What is meant by “Angular acceleration”?

Answer 10

The rate of change of Angular Velocity

Question 11

How to convert between Revolutions and radians

Answer 11

Multiply number of revolutions by 2π

Question 12

What is meant by “Radial acceleration”?

Answer 12

Acceleration towards the centre of a circular path.

Question 13

What is meant by “Centripetal force”?

Answer 13

Any force that acts radially towards the center of a circular path.

Question 14

What is meant by “Torque”?

Answer 14

The moment (angular equivalent) of a force.

Question 15

What is meant by “Angular Momentum”?

Answer 15

The moment (angular equivalent) of linear momentum.

Question 16

What is the “Law of conservation of angular momentum”?

Answer 16

The Total Angular Momentum before a collision will equal the Total Angular Momentum after a collision, as long as no external Torques act upon the system.

Question 17

What is meant by “Gravitational Force”

Answer 17

The Force between two objects with mass. It is proportional to magnitude of the masses, and inversely proportional to the square of the radius between them.

Question 18

What is meant by “Gravitational field strength”?

Answer 18

The force experienced by a unit mass (1kg) at that point in a gravitational field.

Question 19

What is meant by “Gravitational Potential”?

Answer 19

The work done by an external force to move a unit mass from infinity to that point.

Question 20

What is meant by a “Conservative field”?

Answer 20

The energy required to move between two points is independent of the path taken.

Question 21

What is meant by a “Potential well”?

Answer 21

The 3d representation of the changing gravitational potential around a mass.

Question 22

What is meant by “Escape velocity”?

Answer 22

The initial velocity at which an object would have suffient energy to move from its starting radius to infinity.

Question 23

What is meant by the “Schwarzschild radius”?

Answer 23

The radius from the center of an object at which its escape velocity is equal to the speed of light.

Question 24

What is meant by a “Black body object”

Answer 24

An object that is perfect absorber and emitter of radiation.

Question 25

Which type of Fusion occurs within stars on the "Main sequence" of an H-R diagram?

Answer 25

Proton-Proton Chain fusion

Question 26

Which type of Fusion occurs within stars on the "Giant branch" of an H-R diagram?

Answer 26

Fusion of helium and heavier elements

Question 27

Which type of Fusion occurs within stars on the "Dwarf" section of an H-R diagram?

Answer 27

No fusion takes place.

Question 28

What is the end of life point for a low mass star?

Answer 28

(White) dwarf

Question 29

What is the end of life point for a medium mass star?

Answer 29

Neutron star

Question 30

What is the end of life point for a high mass star?

Answer 30

Black hole

Question 31

Which two forces determine the radius of a star?

Answer 31

Gravitational force & Thermal pressure

Question 32

What is meant by a "Non inertial" frames of reference?

Answer 32

Reference frames which are accelerating relative to each other.

Question 33

What is the "Equivalence principle"?

Answer 33

No experiment can differentiate between the effect of a Uniform Gravitational field and an accelerating reference frame.

Question 34

What is meant by a "Geodesic"?

Answer 34

The shortest posssible route through curved Space-Time.

Question 35

Why does "Gravitational redshift" occur?

Answer 35

As the Photon moves away from the Mass, Work must be done to escape the Gravity Well. This causes the Photon's energy to reduce, reducing the frequency.

Question 36

What is meant by "Space-Time"?

Answer 36

A 4-dimensional coordinate system which takes into account that an event will occur at a location with a set 3-dimensional position (x,y,z ) and time (t).