Space - Core

Question 0

What is gravitational potential energy?

Answer 0

It is the energy of a mass due to its position within a gravitational field. On a large scale, gravitational potential energy is defined as the work done to move an object from infinity (or some point very far away, to a point within a gravitational field

Question 1

On Earth, what is the gravitational field strength g?

Answer 1

9.8m.s-2

Question 2

At infinity, what is Ep defined as?

Answer 2

Zero

Question 3

What is a projectile?

Answer 3

Any object moving under the influence of gravity only.

Question 4

What are the two independent motions of projectile motion?

Answer 4

The horizontal (x) component and the vertical (y) component.

Question 5

What is escape velocity?

Answer 5

It is the velocity needed for an object to escape from the Earth (or other planet or moon).

Question 6

What does escape velocity depend on?

Answer 6

The mass of the planet or moon and the gravitational constant, G.

Question 7

What is the trajectory of a projectile?

Answer 7

It is the path that it follows during its flight.

Question 8

What is thrust?

Answer 8

Thrust is the force delivered to a rocket by its engines.

Question 9

What is uniform circular motion?

Answer 9

It is circular motion with a uniform orbital speed

Question 10

What is centripetal force?

Answer 10

It is the force that acts to maintain circular motion and is directed towards the centre of the circle.

Question 11

When is centripetal acceleration present?

Answer 11

Always in uniform circular motion. It is also associated with centripetal force and is also directed towards the centre of the circle

Question 12

What is orbital velocity?

Answer 12

It is the instantaneous direction and speed of an object in circular motion along its path.

Question 13

What is a LEO?

Answer 13

LEO stands for low Earth orbit and it is an orbit higher than 250km and lower than 1000km.

Question 14

What is a geostationary orbit?

Answer 14

A geostationary orbit is at an altitude at which the period of the orbit precisely matches that of the Earth. This corresponds to an altitude of approximately 35800km.

Question 15

What is the slingshot effect, or planetary swing-by or gravity assist manoeuvre?

Answer 15

It is a strategy used with space probes to achieve a change in velocity with little expenditure of fuel.

Question 16

What is the first phase of the de-orbit manoeuvre?

Answer 16

It is to alter the spacecraft’s orbit into a transfer ellipse that intersects the atmosphere at the desired angle.

Question 17

With re-entry, why is a shallow angle selected?

Answer 17

To minimise the extreme heating and g forces that can destroy a spacecraft on an uncontrolled re-entry. However, if the angle is to shallow, the spacecraft may skip off the atmosphere instead of penetrating it.

Question 18

Why is it that re-entry produces so much heat?

Answer 18

Consider that the spacecraft has a velocity of tens of thousands of kilometres per hour. This velocity means that the spacecraft has significant kinetic energy. Additionally, the altitude of the spacecraft’s orbit means that it also has considerable gravitational potential energy, which is also lost as the spacecraft’s altitude decreases during re-entry. As the spacecraft re-enters, it experiences friction with the molecules of the atmosphere. This friction is a force directed against the motion of the spacecraft and causes it to decelerate; that is, to slow down. The enormous kinetic energy the spacecraft possesses is converted into heat, and that heat can cause the spacecraft to reach extreme temperatures.

Question 19

What is Ionisation blackout?

Answer 19

It is a period of no communication with a spacecraft due to a surrounding layer of ionised atoms forming in the heat of re-entry

Question 20

What is a gravitational field?

Answer 20

It is a field within which any mass will experience a gravitational force. The field has both strength and direction.

Question 21

What was the aether?

Answer 21

It was the proposed medium for light and other electromagnetic waves, before it was realised that these waveforms do not need a medium in order to travel.

Question 22

What is a medium?

Answer 22

It is the material through which a wave travels

Question 23

What is an inertial frame of reference?

Answer 23

It is a non-accelerated environment. Only steady motion or no motion is allowed.

Question 24

What is a non-inertial frame of reference?

Answer 24

It is a frame of reference which experiences acceleration.

Question 25

What is a rest frame?

Answer 25

It is the frame of reference within which a measured event occurs or a measured object lies at rest.

Question 26

What is time dilation?

Answer 26

It is the slowing down of events as observed from a reference frame in relative motion.

Question 27

What is length contraction?

Answer 27

It is the shortening of an object in the direction of its motion as observed from a reference frame in relative motion.

Question 28

What is mass dilation?

Answer 28

It is the increase in the mass of an object as observed from a reference frame in relative motion.

Question 29

What is rest energy?

Answer 29

It is the energy equivalent of a stationary object’s mass, measured within the objects rest frame.