Need For Speed Unit Flashcards
What does this speed-time graph show?
Constant velocity
How can you increases friction?
- 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
Describe how a cyclist can streamline themself
- Crouch over the handlebars
- Wear tight lycra clothing
- Specially shaped helmet
What is a balanced force?
Equal forces acting in opposite directions
Newtons 1st Law is about balanced forces, what two things can happen if a balanced force acts on an object?
- Remains stationary
- Travels at a constant speed in a straight line
What is acceleration?
Acceleration is the rate of change of speed or the change in speed per second.
Which line on the graph represents the largest acceleration?
Blue Line - it is the steepest
What is the difference between mass and weight?
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.
What is speed?
Distance travelled per second.
An astronaut has a mass of 50kg. What will happen to the astronauts mass on the Moon?
It stays at 50kg. Mass does not change.
An astronaut has a mass of 50kg. What will happen to the astronauts weight on the Moon?
The weight will decrease as there is a lower gravitaional field strength on the Moon.
What is meant by gravitational field strength?
Force per unit mass
What is meant by an acceleration of 15ms-2 ?
The velocity increases by 15ms-1 every second.
Explain the difference between average and instantaneous speed.
Average speed is over a long period of time, Instantaneous speed is the speed over a very short period of time.
What will an unbalanced force cause?
Acceleration
Explain how to measure acceleration using the equipment shown below and a stop watch.
- 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
What does the area under this speed - time graph give?
The distance travelled.
How can a space rocket be slowed down in space?
Reverse the thrusters to provide an unbalanced force backwards to slow you down.
What are the three effects a force can have?
- Change the speed of the object
- Change the direction of travel of the object
- Change the shape of the object
How can you decrease friction?
- 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
What does this speed-time graph show?
Constant acceleration
What is meant by streamlining?
Streamlining is changing the shape of an object to reduce air/water resistance
An object travels at a constant speed of 10ms-1. What can be said about the forces on it?
The forces are balanced
Explain how a seatbelt works in terms of Newton’s Laws.
- 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)
What causes friction?
Two surfaces rubbing together
What does this speed - time graph show?
Constant de-acceleration
Describe a streamlined shape
- Low to the ground
- Smooth
- Have curves
What does the area under the speed-time graph give?
The distance travelled
Explain how to measure the acceleration of the car using the equipment shown below and a stop watch.
- 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
Describe how to calculate acceleration from a speed - time graph.
- Pick two pints on the slope.
- u = initial speed-read it off the graph,
- v = final speed-read it off the graph,
- t = time to go from the initial to the final speed.
- Then use a = (v-u)/t
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?
4000N backwards
Describe how to measure average speed using the equipment below.
- 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
Explain how to use the equipment below to calculate the instantaneous speed of the car.
- 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
Describe how to measure average speed.
- 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
Explain why the angle of re-entry poses a challenge.
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.
What is meant by a light year?
The distance that light could travel in one year.
Explain why re-entering the atmosphere poses a challenge.
- 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.
What is a geostationary satellite?
Satellites with a period of 24 hours and orbit at a height of 36000km. They remain above the same point on the Earth.
How can you calculate the distance that is one light year?
- d=vt
- d = 3 x 108 x (365.25 x 24 x 60 x 60)
What is an exoplanet?
A planet orbiting a sun outside our solar system.
Using Newton’s 3rd Law explain how a space rocket takes off.
Engines push exhaust gases downwards. Exhaust gases push engines upwards.
What are the two main challenges of re-entry?
- Angle of re-entry
- High temperatures / heating effect
What is a planet?
A ball of mass that orbits a sun
What is a galaxy?
A galaxy is a gravitationally bound system of stars, stellar remnants, gas, dust and dark matter.
An astronaut has a mass of 50kg. What will happen to the astronauts weight on the Moon?
The weight will decrease as there is a lower gravitaional field strength on the Moon.
An astronaut has a mass of 50kg. What will happen to the astronauts mass on the Moon?
It stays at 50kg. Mass does not change.
How can a space rocket be slowed down in space?
Reverse the thrusters to provide an unbalanced force backwards to slow you down.
What is a moon?
A natural satellite
What is Newton’s 3rd Law?
For every action force there is an equal but opposite reaction force
How can you work out the resultant force acting on a space rocket at launch?
Resultant force = Engine thrust - (Weight + frictional forces)
Why is manoeuvring in space such an issue?
There is no friction to slow down.
What is a solar system?
It is a system bound by gravity, made up of a sun and the planets that orbit it.
What is meant by gravitational field strength?
Force per unit mass
What is a sun?
A star is called a sun if it is the centre of a planetary system.
What is a star?
A ball of gas undergoing fusion that gives off heat and light.
What are the forces acting on a space rocket at launch?
- Weight - downwards
- Friction/air resistance - downwards
- Engine thrust upwards
What is the difference between mass and weight?
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.
How is the period of a satellite effected by the orbiting altitude/height?
The bigger the orbiting altitude / height the longer the period orbit.
What is meant by the universe?
The universe is all of time and space and its contents.
Should the engine force or the resultant force be used when calculating the acceleration of a space rocket on take off?
Resultant force
What is an exoplanet?
A planet outwith our solar system.
What does an exoplanet need to sustain life?
Liquid water.
State two things that the Hubbles Space Telescope has given us information about.
- 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.
State three uses for satellites
- Telecommunications
- Monitoring weather
- Mapping
- GPS
- Monitoring environmental change (desert size, ice sheets)
Why is a curved reflector used to receive signals?
- Collects a large amount of signal
- Focuses it onto a detector.
Why is a curved reflector used to transmit signals?
It gives a parallel beam of signal that can be directed.
What would a diagram look like to show the effect of a curved reflector being used as a transmitter?
See diagram
What would a diagram look like to show the effect of a curved reflector being used as a receiver?
See diagram
What is a radiotelescope?
A radio telescope detects radio waves from distant planets / stars.
State the effect of increasing the diameter of the objective lens of a refracting telescope.
The image would be brighter
What affects the magnification of a refracting telescope?
The lenses chosen as the objective and eyepiece lenses.
What is the purpose of the light tight tube in a refracting telescope?
Cuts out light from other sources
What is meant by density?
Mass per unit volume
Which device can measure density?
Hydrometer
What is the name of the device that an object can be dropped into and water comes out? The volume of water that comes out is equal to the volume of the object.
Eureka Can
What does d stand for and what is it’s unit?
distance in metres, m
What does v stand for and what is it’s unit?
speed, metres per second, ms-1
What does t stand for and what is its unit?
time in seconds,s
What does a stand for and what is its unit?
acceleration in metres per second per second, ms-2
In the acceleration formula what does u stand for?
Initial speed in metres per second, ms-1
In the acceleration formula what does v stand for?
Final speed in metres per second ms-1
In the acceleration formula what does t stand for?
The time for the change in speed in seconds, s
What does W stand for and what is its unit?
Weight in Newtons, N
What does m stand for and what is its unit?
Mass in kilograms, kg
What does g stand for and what is its unit?
Gravitational field strength in Newtons per kilogram, Nkg-1
What does F stand for and what is its unit?
Unbalanced force in Newtons, N
What does p stand for and what is its unit?
density in kilograms per cubic metre, kgm-3
What does V stand for and what is its unit?
Volume in cubic metres, m3
Explain when an object will float in terms of density
If the density of the object is less than the density of the water
How do you calculate a light year?
d = vt
d = 3 x 108 x (365.25 x 24 x 60 x60)
