# Dynamics and Space Whole Unit Flashcards Preview

## Harris Academy N4 Physics > Dynamics and Space Whole Unit > Flashcards

Flashcards in Dynamics and Space Whole Unit Deck (64)
1
Q

Describe how to measure average speed.

A
• Mark a start line and a finish line.
• Measure the distance between the start and finish line with a ruler/metre stick.
• Start a stopwatch when the object crosses the start line and stop it when the object crosses the finish line.
• Calculate the average speed = distance between start and finish / time on stopwatch
2
Q

Describe how to measure average speed using the equipment below.

A
• Two light gates are connected to a timer.
• The car rolls down the slope.
• When the cardboard breaks the first lightgate beam it starts the timer. When the cardboard breaks the second lightgate beam it stops the timer.
• The timer records the time taken to go from the first to the second light gate.
• Measure the distance between the two light gates using a metre stick.
• Calculate the speed = distance between light gates / time on timer
3
Q

Explain how to use the equipment below to calculate the instantaneous speed of the car.

A
• Measure the length of the cardboard using a ruler.
• Roll car down the slope.
• When the cardboard breaks the beam it starts the timer connected to the light gate. When the cardboard has passed through the beam is remade and the timer stops.
• Speed = length of cardboard / time on timer
4
Q

Explain the difference between average and instantaneous speed.

A

Average speed is over a long period of time, Instantaneous speed is the speed over a very short period of time.

5
Q

What is the difference between a vector and a scalar quantity?

A

A scalar needs size/magnitude to be described correctly. A vector needs size/ magnitude and direction to be described correctly.

6
Q

What is speed?

A

Distance travelled per second.

7
Q

What is acceleration?

A

change in velocity per second.

8
Q

What is meant by an acceleration of 15ms-2 ?

A

The velocity increases by 15ms-1 every second.

9
Q

Explain how to measure the acceleration of the car using the equipment shown below and a stop watch.

A
• Car starts from rest so u = 0ms-1.
• When the car is released start the stop watch when it reaches the light gate stop the stop watch.
• This is t, the time for the change in velocity.
• When the cardboard passes through the light gate the timer attached to it records this time.
• Measure the length of the card with a ruler.
• The final velocity, v = length of card / time on timer
• Then calculate acceleration, a = (v-u)/t
10
Q

Explain how to measure acceleration using the equipment shown below and a stop watch.

A
• When the cardboard passes through the first light gate the timer attached to it records this time.
• Measure the length of the card with a ruler.
• The initial velocity, u = length of card / time on timer
• As the car rolls down the ramp, start the stop watch when it reaches the first light gate and when it reaches the second light gate stop the stop watch.
• This is t, the time for the change in velocity.
• When the cardboard passes through the second light gate the timer attached to it records this time.
• The final velocity, v = length of card / time on timer
• Then calculate acceleration, a = (v-u)/t
11
Q

What does this speed-time graph show?

A

Constant speed

12
Q

What does this speed-time graph show?

A

Constant acceleration

13
Q

What does this speed - time graph show?

A

Constant de-acceleration

14
Q

Describe how to calculate acceleration from a veocity - time graph.

A
• Pick two pints on the slope.
• work out the change in speed,
• t = time to go from the initial to the final speed.
• Then use a = ∆v/t
15
Q

What are the three effects a force can have?

A
• Change the speed of the object
• Change the direction of travel of the object
• Change the shape of the object
16
Q

What is a balanced force?

A

Equal forces acting in opposite directions

17
Q

Newtons 1st Law is about balanced forces, what two things can happen if a balanced force acts on an object?

A
• Remains stationary
• Travels at a constant speed in a straight line
18
Q

An object travels at a constant speed of 10ms-1. What can be said about the forces on it?

A

The forces are balanced

19
Q

What causes friction?

A

Two surfaces rubbing together

20
Q

How can you increases friction?

A
• Increase the area of the rubbing surfaces
• Make the rubbing surfaces rougher
• Push the rubbing surfaces togerther more
• Increase the speed that the surafces are rubbed together
21
Q

How can you decrease friction?

A
• Decrease the area of the rubbing surfaces
• Make the rubbing surfaces smoother
• Push the rubbing surfaces together less
• Decrease the speed that the surfaces are rubbed together
• Lubricate/oil/ wax the surfaces
• Streamline the object
22
Q

What is meant by streamlining?

A

Streamlining is changing the shape of an object to reduce air/water resistance

23
Q

Describe a streamlined shape

A
• Low to the ground
• Smooth
• Have curves
24
Q

What will an unbalanced force cause?

A

Acceleration

25
Q

Explain how a seatbelt works in terms of Newton’s Laws.

A
• When a car travels at a constant velocity the forces on it are balanced. (Newtons 1st Law)
• If the brakes are applied they provide an unbalanced force that stops the car. (Newtons 2nd Law)
• The passengers continue to travel at a constant speed in a straight line. (Newtons 1st Law)
• The seatbelt provides an unbalanced backwards force to decelerate the passenger to zero without hitting the windscreen. (Newtons 2nd Law)
26
Q

What is the difference between mass and weight?

A

Mass is a measure of the partcles that make an object up. Weight is a force caused by the gravitational field strength of a planet.

27
Q

What is meant by gravitational field strength?

A

Force per unit mass

28
Q

An astronaut has a mass of 50kg. What will happen to the astronauts mass on the Moon?

A

It stays at 50kg. Mass does not change.

29
Q

An astronaut has a mass of 50kg. What will happen to the astronauts weight on the Moon?

A

The weight will decrease as there is a lower gravitaional field strength on the Moon.

30
Q

Describe how a cyclist can streamline themself

A
• Crouch over the handlebars
• Wear tight lycra clothing
• Specially shaped helmet
31
Q

A car is travelling at a constant velocity of 25ms-1, the engine is producing a force of 4000N. What is the size of the frictional forces acting on the car?

A

4000N backwards

32
Q

Which line on the graph represents the largest acceleration?

A

Blue Line - it has the steepest gradient

33
Q

What are the possible dangers of space exploration?

A
• Training accidents
• Fire
• Rocket malfunction
• Vehicle Break-up
• On board explosion
• Depressurisation
• Space suit failure
• Control failures
• Heat shield failure
• Parachute failure
34
Q

What are the two main challenges of re-entry?

A
• Angle of re-entry
• High temperatures / heating effect
35
Q

Explain why the angle of re-entry poses a challenge.

A

The angle of re-entry to the atmosphere is important

• too steep and the change in kinetic energy being transferred to heat is too fast resulting in overheating and possible rocket break-up
• If the angle is too shallow you will skip off the atmosphere.
36
Q

Explain why re-entering the atmosphere poses a challenge.

A
• When a space craft is in space there is no friction as space is a vacuum.
• When you re-enter the Earth’s atmosphere you go from no friction to lots of friction (caused by the atmosphere).
• The result is that the space craft loses kinetic energy and slows down.
• However due to conservation of energy, the energy is not lost but is converted to heat.
• The outside of the space craft becomes incredibly hot.
• This means that the space vehicle requires thermal shielding.
37
Q

List some benefits of space exploration.

A
• Satellite communications
• GPS and SatNav technologies
• Weather forecasting / storm tracking
• Improved mapping
• Spin off technologies - hand held drills, portable DVD players, memory foam
38
Q

Name one man made objects that have helped us explore space.

A
1. Hubble Space Telescope
2. Voyager Probes
3. Cassini - Huygens
39
Q

State two things that the Hubbles Space Telescope has given us information about.

A
• Determining the age of the universe to 13 to 14 billion years
• Key role in discovering ‘dark energy’ (a mysterious force that causes the expansion of the universe to accelerate)
• Produced images of galaxies in all stages of evolution – helps understanding of galaxy formation.
• Discovery of gamma ray bursts occur in far off galaxies when massive stars collapse.
• Hubble provided evidence that supermassive black holes exist
• Hubble has made detections of the atmosphere of a planet orbiting a star outside the solar system and obtained information about its chemical composition. It determined it was not suitable for life.
40
Q

State two things that the Voyager Probes have given us information about.

A
• Capturing the Earth and Moon together for the first time
• Finding moons “shepherding” Saturn’s F ring
• Spotting what appeared to be a LOT of water ice on Saturn’s moons
• Imaging Titan’s orange haze
• Finding active volcanoes on Io
• Information about moons - At Io — a moon of Jupiter — it turns out the moon flexes during its 42-hour orbit of massive Jupiter, which powers a lot of volcanic activity.
• Discovering new regions of space
41
Q

State two things that the Cassini - Huygens probe has given us information about.

A

• The rings are made of fragments of ice and rock.
• There are thousands of concentric rings
• The rings have formed recently, after crashes between asteroids and some moons.
• A moon of Saturn, Enceladus has water.
• A moon of Saturn, Titan has lakes of methane and crio-volcanoes.
42
Q

What is the ‘observable universe’?

A

The observable universe is the furthest point that we can ‘see’ or detect. The furthest point that we can ‘see’ is the distance which light must have travelled for the whole age of the universe.

43
Q

What is meant by a star?

A

A ball of burning gas

44
Q

What is meant by a planet?

A

An object that orbits a star

45
Q

What is meant by a moon?

A

An object that orbits a planet

46
Q

What is a star and it’s orbitting planets called?

A

Solar system

47
Q

What is an exoplanet?

A

A planet ouwith our solar system

48
Q

What is a galaxy?

A

Vast collections of stars, gas, dust held together by gravity

49
Q

What is a ball of burning gas?

A

Star

50
Q

What is an object that orbits a star?

A

Planet

51
Q

What is an object that orbits a planet?

A

moon

52
Q

What is a star and it’s orbitting planets called?

A

Solar system

53
Q

What do you call a planet outside our solar system?

A

Exoplanet

54
Q

What is a vast collections of stars, gas, dust held together by gravity called?

A

Galaxy

55
Q

What is a light year?

A

The distance that light can travel in one year

56
Q

Why do we use light years?

A

Distances in space are so huge we need a big unit to measure it in.

57
Q

What does an exoplanet need to sustain life?

A

Liquid water

58
Q

What is a geostationary satellite?

A

A satellite that remains above the same point on the Earth

A satellite that has a period of 24 hours

59
Q

State three uses for satellites

A
• Telecommunications
• Monitoring weather
• Mapping
• GPS
• Monitoring environmental change (desert size, ice sheets)
60
Q

What effect does height above the Earth have on a satellite?

A

The higher the satellite the longer it takes to orbit the Earth

61
Q

Why is a curved reflector used to receive signals?

A
• Collects a large amount of signal
• Focuses it to a point
62
Q

Why is a curved reflector used to transmit signals?

A

It gives a parallel beam of signal that can be directed.

63
Q

What would a diagram look like to show the effect of a curved reflector being used as a transmitter?

A

See diagram

64
Q

What would a diagram look like to show the effect of a curved reflector being used as a receiver?

A

See diagram