Motion and Space

Question 1

What is weight measured in?

Answer 1

Newtons

Question 2

What is the equation for weight?

Answer 2

F = mg

Question 3

Define weight.

Answer 3

The force on an object due to a gravitational field.

Question 4

What is the equation of the law of universal gravitation?

Answer 4

F = Gm1m2/d^2

Question 5

What does G stand for in:

F = Gm1m2/d^2

Answer 5

The Gravitational Constant

Question 6

Define work.

Answer 6

Work is an exertion of force that changes the energy of an object.

Question 7

What is the equation used to calculate work.

Answer 7

W = Fs

Question 8

What two factors are primarily responsible for the measured value of gravity varying across the Earth’s surface?

Answer 8

As the Earth is not an inertial frame of reference, the closer you are to the equator, the further you are from the Earth’s axis of rotation, and the larger the perceived upwards centrifugal force will act upon you.

The Earth is a spheroid, wider at the equator, so gravity has a slightly weaker effect at the equator.

Question 9

What is the equation for gravitational potential energy?

Answer 9

E(p) = -Gm1m2/r

Question 10

What is the trajectory of an object undergoing projectile motion?

Answer 10

A parabola

Question 11

Why is gravitational potential energy negative?

Answer 11

It increases as you get further away from the object, but is zero at an infinite distance.
Therefore, it is negative, and increases as it moves away from an object until it gets to zero.

Question 12

Define gravitational potential energy.

Answer 12

The work done by a gravitational field to move an object from from an infinite distance away to a point within the field.

Question 13

Describe the motion of an object undergoing projectile motion in terms of it’s horizontal and vertical components.

Answer 13

Projectile motion involves constant horizontal motion and vertical accelerated motion.

Question 14

What was he major discovery of Galileo’s analysis of projectile motion?

Answer 14

Horizontal and vertical movement are independent of each other.

Question 15

Explain escape velocity in terms of the gravitational constant and the mass and radius of the planet.

Answer 15

Escape velocity is the speed where the kinetic energy of an object is equal to the magnitude of its gravitational potential energy.

Question 16

Outline Newton’s concept of escape velocity.

Answer 16

At a certain speed, a projectile will fall in a circular orbit around the Earth.

Question 17

Outline von Braun’s contribution to the development of space exploration.

Answer 17

Proved gyroscopes could stabilise rockets.
Developed the V2 and three-stage rockets.
Constructed the first Saturn rocket which would lead to landing astronauts on the moon.

Question 18

Make a judgement on the significance of von Braun’s contributions to space exploration.

Answer 18

His contributions were very significant as his work on multistage rockets provided the reduction in g forces required to send astronauts into space.

Question 19

Identify what the term g force means and why it used.

Answer 19

G force refers to the size of the reaction force acting on a person, creating the illusion of a different direction of gravity.

Question 20

Identify three ways to increase the placing of a rocket in orbit.

Answer 20

Launch east, as the Earth rotates east.
Launch at low latitude, as the speed is greatest at the equator.
Launching at night as the orbital speed will be added.

Question 21

Analyse the changing acceleration of a rocket during launch in terms of the Law of Conservation of Energy.

Answer 21

The momentum the rocket gains must be equal in magnitude and opposite in direction to the momentum of the rocket.

Question 22

What equation gives the centripetal force acting on an object.

Answer 22

F(c) = mv^2/r

Question 23

What equation gives the acceleration due to the centripetal force acting on an object.

Answer 23

A(c) = v^2/r

Question 24

Compare low earth and geostationary orbits.

Answer 24

Low Earth Orbit is 250-1000km high, geostationary is 35,000km high.
Low Earth Orbit orbits in 90 minutes, geostationary orbits in a day.
Low Earth Orbit is thousands of kilometres fast, geostationary is 3km/hour.
An example of LEO is the Hubble Telescope, and example of geostationary is a weather satellite.

Question 25

What is the equation that relates the radius and period of an orbit to the mass of its central body?

Answer 25

r^3/T^2 = GM/4(Pi)^2

Question 26

State the equation for determining orbital velocity.

Answer 26

v = 2(Pi)r/T

Question 27

State Kepler’s law of periods.

Answer 27

The ratio of r^3/T^2 is constant for everything orbiting a central body.

Question 28

Describe the two main issues of safe re-entry into Earth’s atmosphere.

Answer 28

Heat due to the friction and compression of air in front of the craft can cause structural damage to the craft.

G-Forces must be kept to levels at which the astronauts can survive and the craft will remain stable.

Question 29

What is optimum angle for safe re-entry of a spacecraft and what are the consequences of not achieving this angle?

Answer 29

5.2 - 7.2 degrees for Apollo missions.

If the angle is too shallow the craft may skip off the atmosphere, lose speed, and then return at a steep angle.

Question 30

Define a gravitational field.

Answer 30

A region surrounding an object with mass.

Question 31

Define Newton’s Law of Universal Gravitation.

Answer 31

All bodies with mass create a gravitational force.
The force is proportional to the mass of each body.
The force is inversely proportional to the distance between the bodies’ centres.

Question 32

What is the equation for Newton’s Law of Universal Gravitation?

Answer 32

F = Gm(1)m(2)/d^2

Question 33

State the importance of Newton’s Law of Universal Gravitation in calculating the orbits of satellites.

Answer 33

The force of gravity is the only force acting on satellites, hence the path a satellite will follow can be calculated using Newton’s Law of Universal Gravitation.

Question 34

Describe the slingshot effect.

Answer 34

A gravitational slingshot is when the gravity of another celestial body is used to alter the path or speed of a spacecraft.