Things You Got Arong Gcse Revision Flashcards
What does flat line represent on velocity time graph. State two meanings
Constant velocity.
No acceleration
What does a curved line represent on distance time graph
Acceleration (speed is changing)
Give examples of 8 types of forces
-air resistance
-friction
-upthrust
-gravitional
-electrostatic
-compression (squeezing together)
-tension(stretching)
-reaction force
What three effects do forces have
Change speed
Change direction
Change shape
Icy rod conditions,travelling fast, worn out tyres all affect stopping distance.
Name one more feature that can affect stopping distance
Vehicle mass
What does a negative resultant force mean
Acts in opppostion to objects motion and so therefore slows them down
Small mass means….. acceleration because ….
More
Because mass is inversely promotional to acceleration
What three things can an unbalanced force do to an object
Causes it to accelerate so can,
-slow down
-speed up
-change direction
As speed of an object increase increases why does its air resistance increase
Because there is friction between the objects motion, and collisions with the air particles
So the air particles try to slow it down, called air resistance
Explain why when opening a parachute, velocity begins to decrease until a terminal velocity is reached
-air resistance is greater than weight
-this causes an upwards resultant force
-this causes deceleration, so the velocity begins to decrease (slows down)
-when velocity decreases, air resistance also decreases
-therefore air resistance and weight are now equal
-and object has reached terminal velocity
State the equation for hooks law, and state what hooks law is
F=Kx
That the force applied to an object is directly proportional to its extension, UP UNTIL THE LIMIT OF PROPORTIONALITY
How do you calculate the extension of a spring
New reading on ruler- reference point(intitial reading)
Describe the experiment for hooks law
1) set up a clamp and stand, and attach a spring without any masses to it
2)place a ruler next to it, MAKE SURE TO MEASURE AT EYE LEVEL TO AVOID PARRALEX ERROR, and measure intitial length of spring
CAN IMPROVE ACCURACY USES A FIDUCIAL MARKER
3)Add one mass at a time, and measure the new length of spring
4)calculate extension by doing new length- original length
5)repeat for increasing masses
6)then repeat whole experiment again three times and take an average
7)plot a graph to show with force on y axis and extension on x axis
Give a statement sthat links momentum and force
Force is the rate of change of momentum
What is a moment
The turning effect of a force, about a pivot
Principle of moments
If an object is balanced, the total clockwise moments equals the total anti clockwise moments about a pivot
Explain how a freely suspended object swings, in terms of moments and centre of gravity
-the objects weight acts at a distance from the pivot, which is the suspension point
-this creates a moment
-which causes it to swing
-and so the centre of gravity will now be directly vertically below the suspension point
Explain how to find the centre of gravity for an irregular shaped object
1)draw the point of suspension and suspend from that point, and suspend a plumb line for the same point, and wait until it stops moving
2)draw a line down the plumb line
3)suspend from another point with a plumb line and draw another line
4)the centre of gravity will be where the both lines intersect
What is the centre of gravity
The point through which the weight of the object acts
On a distance time graph, if a gradient becomes steeper this means,…
And if a gradient becomes less steep this means,…
Speed increases
Speed decreases
What does constant acceleration mean
That the velocity increases at a constant rate
If the driving force is the same of a car, state two reasons why the car could still experience a change in acceleration
Air resistance increases
Friction increases
Describe the difference between average speed and instantaneous speed
Average speed= total distance/total time, assumes that speed is constant and no acceleration
Instantaneous speed= speed at a particular moment. Can vary between two different parts of a ramp bc may have accelerated
Explain the difference in method between calculating the average speed of a car on a ramp
And calculating the speed at the bottom of the ramp
Average speed= measure time it leaves the top and the time it reaches the bottom
Then do distance divided by time
Speed at the bottom of the ramp is done using light gates, with a card on the car to detect it, connected to a computer. So light gates measure the time at the particular moment that it reaches the bottom
Then speed equals total distance divided by that time
What does a low terminal velocity suggest about the rate that an object falls at
It means that it falls at a much slower rate than an object that has a high terminal velocity
Because this means that it reaches constant speed much quicker than the one with high terminal velocity
So spends less time accelerating downwards
give the colours in a ring main circuit and what each one represents
blue, neutral wire
green yellow, earth wire
brown, live wire
if double insulation is present, is earthing required or not and explain why
double insulation means all parts of the wire are insulated,
therefore the earth wire would not be able to conduct a current, and so would not be needed.
explain how a fuse works, and give advantages and disadvantages of circuit breakers.
fuse contains a thin metal wire which melts when current is too high due to its low boiling point. this stops the current and so user can’t conduct an electric shock.
circuit breakers, doesn’t have to be replaced, more sensitive to changes
Explain how fueling aircraft can be dangerous and how this can be tackled
When aircraft is flying, friction with the air causes a charge to build up
So if a lot of charge has build up, it can escape to the earth and cause a spark to built up
And when refueling this spark can cause an explosion
Therefore earthing can be done which provides an alternative pathway the ground, and so removes the excess charge from the aircraft
Explain how a photocopier works
An image of the document is reflected onto the turning drum
The turning drum is positively charged, and is an insulator in dark area, and a conductor in light areas
So the area that is light gets discharged, and the dark area on the paper remain negatively charged
This then passes through to a toner which is positively charged, and so black powder sticks to this area
The image is then transferred to white paper
And is heated so that the toner sticks to the paper
Explain how to use an oscilloscope to measure the speed of sound in air
1) set a set frequency on a signal generator
2)attach two microphones to an oscilloscope which are equal distance away from each other
3)keep moving one microphone back until the waves for each microphone on the oscilloscope are synchronized, (because this is one wave length)
4)measure the distance between the two microphones
5) use equation V=FH
Explain how optical fibres work in endoscopes
Endoscopes contains a bundle of fibres
Light enters from an angle of incidence that is greater than the critical angle,
So it is totally internally reflected throughout the tube each time it hits the edge
Give two reasons why optical fibres are more useful in telecommunication rather than copper wires
Because they are thin so can transfer more information
They use less energy than copper
Give four ways to improve accuracy when doung the glass block experiment for refraction
-use a set square to ensure that the normal is completely perpendicular
-when drawing angles use a protractor with a higher resolution
-to ensure accurate values plot a graph for sin i against sin r
-take a mean value
What is the range of human hearing
20-20000HZ
Why can light waves not travel through a vaccum but sound waves can
Light waves need a medium to propagate through but sound waves do not
Give 4 properties of em waves
All transverse waves
All can be refracted and reflected
Can travel at speed of light in a vacuum
All transfer energy
Explain in terms of the Doppler effect what happens when a sound is heard from near by
The wavefronts are more squashed together
Therefore the wave length decreases
And so the frequency also decreases
Give some uses of radio waves and why
Give some uses of microwaves and why
Radio; radio and broadcasting communication. Bc can be reflected from earths atmosphere
Microwaves; cooking and satellite communication; bc can penetrate earths atmopshere
Give a hazard of microwaves
Give a hazard of visible light
Microwaves can penetrate human body tissue
Visible light can cause blindness if too bright