Nat 5, NAB, January'15 Flashcards
What is meant by the period of a satellite?
The time taken for the satellite to complete one orbit.
How does the period of a satellite depend on the height of its orbit?
The higher the orbit of the satellite, the greater the period and vice versa.
At what speed do radio (or microwave) signals travel during satellite communication?
300,000,000 ms-1
Name 3 applications of satellites
Sending television or radio signals across a country or to another country
Navigation
Weather monitoring
Describe how parabolic (curved) reflectors are used in satellite communication to transmit signals?
Used to transmit a stong, parallel signal beam.
In a dish transmitter, the transmitting aerial is placed at the focus and the curved shape of the reflector produces a parallel signal beam.
Describe how parabolic (curved) reflectors are used in satellite communication to receive signals?
Used to increase the strength of a received signal from a satellite or other source.
The curved shape of the reflector collects the signal over a large area and brings it to a focus. The receiving aerial is placed at the focus so that it receives a strong signal.
How can a satellite be used to monior environmental changes on the Earth?
Used to detect worldwide changes:
The effects of global warming
depletion in the ozone layer
large scale changes in land cover.
How can projectile motion be treated as two independent motions?
Vertical and horizontal.
How do you carry out calculations of projectile motion using appropriate formulae and graphs?
Horizontal)
horizontal displacement= horizontal velocity x time (s=vt)
Vertical)
v= u+ at (u=0 , a=g= 9.8ms-2 on Earth)
Explain how a satellite orbits in terms of projectile motion.
A satellite is continually accelerating vertically towards the ground. However, the satellite is moving so fast horizontally that the Earth curves away from it as quickly as it falls. This means that the satellite never reaches the Earth but continues to move in orbit.
How many metres are in a light year?
9,460,800,000,000,000 metres
How do you calculate the number of metres in 1 light year?
d=?
v= 300,000,000 ms-1
t= 1 x 365 x 24 x 60 x 60
then use d=vt
What is the name of the theory of the origin of the universe?
The big bang theory.
What happened when the universe began?
The entire Universe was inside a hot, dense bubble. There wasn’t actually an explosion, the bubble began to expand.
What evidence is there to support the hot big bang model of the universe?
Galaxies appear to be moving away from us.
The abundance of the elements.
How old do we think the universe is and what evidence is there to suggest the age of the universe?
14 blillion years. It was estimated by looking for the oldest stars and measuring the expansion of the universe.
What is the electromagnetic spectrum?
A group of radiations which have given astronomers a vast amount of information on the Universe.
What do all the waves in the electromagnetic spectrum have in common?
All radiations travel at the speed of light (=300,000,000ms-1)
List the waves of the electromagnetic spectrum in order of frequency?
(increasing) Radio and TV waves Micro waves Infra Red Visible light Ultra Violet X-Rays Gamma Rays
List the waves of the electromagnetic spectrum in order of wavelength?
(increasing) Gamma Rays X-Rays Ultra Violet Visible light Infra Red Micro waves Radio and TV waves
Name an example of a decector for each of the waves in the electromagnetic spectrum.
Radio and TV- Aerial Micro waves- Diode probe Infra Red- Blackened thermometer Visible Light- Photographic film Ultra Violet- Fluorescent paint X-Rays- Photographic film Gamma Rays- Geiger- Muller tuber
Why have astronomers developed telescopes to detect different parts of the electromagnetic spectrum?
So they can find out information about stars from the light the star emits.
What information hae astronomers obtained from using these telescopes?
They have identified elements present in distant stars.
What have we learned about planet Earth as a result of space exploration?
A greater understanding about the rotation of the Earth.
Allowed meteorologists predict and monitor the weather.
Allowing monitoring of the polar ice caps.
What have we learned about the Universe as a result of space exploration?
Greater understanding of the origin of the Universe.
That the universe is still expanding.
Estimate the age of the Universe.
How has our model of the Universe changed over time?
People believed;
the Earth was flat (it’s round)
The Earth was the centre of the Universe (it’s not)
The Sun was the centre of the Universe (it’s not)
The Milky Way was the centre of the Universe (it’s not)
Apply Netwon’s Second Law (F=ma) to describe the motion and the forces acting on a space rocket during launch
F= ? m= 20,000kg (acting downward, weight) a= 12 ms-2 (opposite of weight)
Apply Netwon’s Second Law (F=ma) to describe the motion and the forces acting on a space rocket during motion in space
Accelerating - forward thrusters on and the forces are unbalanced in the forward direction
Decelerating- backward thrusters on and the forces are unbalanced in the backward direction
What are 4 technologies that were developed as a result of space exploration?
Artificial limbs, ear thermometers, water purification, heat resistant paints.
List the benefits associated with space exploration.
That many items have been discovered/ created that benefit everyone in our daily lives because of exploration.
What is meant by the term specific heat capacity?
The amount of energy required when a 1kg substance changes in temperature by 1’C without changing the state of the substance.
What is meant by the term change of state?
Energy is either added or given out.
What is meant by the term specific latent heat of fusion?
The amount of energy required or given out when 1kg of a substance changes state from a solid to a liquid or a liquid to a solid without changing the temperature of the substance.
What is meant by the term specific latent heat of vaporisation?
The amount of energy required or given out when 1kg of a substance changes state from a liquid to a gas or a gas to a liquid without changing the temperature of the substance.
What is the equation used when solving a specific heat question?
Heat energy= specific heat capacity x mass x change in temperature
Eh= cm (Delta) T
What happens to the temperature of a substance when it changes state?
There is no change in temperature until the change of state is complete.
What happens to the energy of a substance when it changes state?
Energy is either given out or added.
Describe the need for thermal protection systems to protect spacecraft during re-entry?
The craft is travelling at about 8000ms-1 and a large frictional force acts on it due to the air in the atmosphere. The frictional force causes a rise in temperature.
Describe the challenges of re-entry to the Earth’s atmosphere?
Rise in temperature due to friction
The angle of re-entry
Make a list of the risks associated with space exploration?
Expensive
Risky (deadly)
What is meant by the term speed?
The distance travelled by an object per second.
How do you find the average speed?
v= d/t
Describe how to measure an average speed
Mesure the distance travelled with a measuring tape. Measure the time taken for the vehicle to travel the distance with a timer.
Use v= d/t to calculate the average speed.
Describe how to measure an instantaneous speed
Measure the length of the vehicle with a measuring tape.
Measure the time taken for the vehicle to pass a point with a light gate connected to a timer.
Use v= d/t to calculate the instantaneous speed
How do you calculate the instantaneous speed of an object?
v= d/t
What is meant by a scalar quantity?
Described by stating it’s magnitude only
What is meant by a vector quantity?
Described by stating it’s magnitude and direction
What are the scalar quantities?
Distance, Speed, Mass, Time, Energy
What are the vector quantities?
Displacement, Velocity, Force, Acceleration
What is the difference between distance and
displacement?
Distance is the total distance travelled regardless or direction.
Displacement is the length measured from the start point to the end point in a straight line. The direction must be stated.
What is the difference between speed and velocity?
Speed is the distance travelled per second.
Velocity is the displacement of an object per second.
What is meant by the term acceleration?
Acceleration is the change in speed or velocity every second.
From a speed time graph, how do you calculate the distance travelled by an object?
Area under the speed time graph
From a velocity time graph, how do you calculate the displacement of an object?
Area under the velocity time graph
When a force is applied to an object, what effect will it have on it?
Change the shape
Change the speed
Change the direction of movement
Define the Newton.
The force required to accelerate a mass of 1kg at a rate of 1ms-2
Is force a vector or a scalar quantity?
Vector quantity.
In which direction does friction act in relation to the motion of an object?
The opposite direction to motion.
What is meant by the term balanced forces?
Two forces which are equal in size which act in opposite directions.
What is meant by the resultant of a number of forces?
When several forces are acting on an object, they can be replaced by a single force.
Explain how an object travels at a constant speed (Newton’s first law of motion)
According to Newton's first law of motion, an object will remain at rest or travel in a straight line at a constant velocity or speed if the forces are balanced. So if (engine) force= friction it will continue to move at a constant velocity or speed in the same direction.
What will happen to the acceleration of an object if only the mass changes?
If the mass increases, the acceleration decreases
vice versa
What will happen to the acceleration of an object if only the force changes?
If the force increases, the acceleration increases
vice versa
Use Newton’s laws to explain the motion of an object during free-fall
During free fall the acceleration is decreasing because weight is greater than air resistance (weight> air resistance) and according to Newton’s second law of motion, if the forces are unbalanced, the object cannot remain at a constant speed.
Use Newton’s laws to explain why an object reaches terminal velocity
An object reaches terminal velocity because, when the object is dropped, the forces are unbalanced because weight> air resistance. According to Newton’s 2nd law of motion (F=ma), if the forces are unbalanced the velocity cannot remain constant. As the object is accelerating downward, the air resistance is increasing until weight= air resistance. According to Newton’s 1st law of motion, the object will remain at a constant speed if the forces are balanced (weight= air resistance), which is called the terminal velocity.
What is work done a measure of?
The energy transformed
What is weight an example of?
Force
What does weight mean?
A force caused by gravity acting on an object’s mass (W= mg)
What is meant by gravatational field strength?
The weight per unit mass of an object.
What equation should be used to find weight?
W= mg
What is Newton’s Third Law of motion?
If object A exerts a force (the action) on obejct B, then object B will exert an equal, but opposite force (the reaction) on object A.
