Y8:Phy6.1 Flashcards
(98 cards)
1
Q
Speed is — and has units—.
A
the distance divided by time; m/s or km/h
2
Q
In UK and USA, speeds are usually measured in–.
A
mph (=miles per hour)
3
Q
3 kinds of speed
A
steady s (speed X change)
average s (total distance/ total time)
instantaneous s (speed at particular moment)
4
Q
precision is shown by the number of –. (-=)
A
Significant figures ( the numbers of digits in a number )
5
Q
precision
A
The number of decimal places given for measurement
6
Q
accuracy
A
How close a measurement is to a true value
7
Q
When – was first introduced, the measure times for the 100 m got -! When the stopwatch was used there was —. This - is called –. (=–)
A
automatic timing; longer;a short delay between the judge hearing the gun and starting the stopwatch; delay; reaction time; the time that it takes the brain to process information (0.2 sec)
8
Q
how does automatic timing works (3)
A
The starter’s gun triggers the start of the timer
the athlete breaks a light beam when their body crosses the line
the light sensor automatically stops the clock.
9
Q
distance-time graph (2)
A
measure the distance a moving object has travelled from its starting point each second
plot a distance-time graph
10
Q
When the speed does not change, the graph–
A
is a straight line.
11
Q
The slope, or -, of a distance-time graph tells you –.
When the slope is flat, the speed is —, and the object–.
A
gradient; the speed
zero, is not moving
12
Q
A more realistic graph would have - lines as our speed change —.
A
curved; gradually (we don’t suddenly change speed)
13
Q
A distance-time graph for a falling ball will – because –. It is a –. This shows that the speed is -.
A
not be a straight line; the speed is not constant; a curve and the slope is increasing; increasing (acclerating)
14
Q
acceleration= (units:)
A
final speed (v) -initial speed(u)/ time m/s^2
15
Q
If the final speed is —, it means that the object is slowing down or decelerating. The acceleration is -.
A
lower than the starting speed; negative.
16
Q
- The gradient of a line on a distance-time graph tells you about –.
- The gradient of a line on a speed-time graph tells you about –.
A
the speed of an object; its acceleration
17
Q
- A straight, sloping line on a speed-time graph shows –.
- A horizontal line on a speed-time graph shows –.
A
constant acceleration; constant speed
18
Q
When the line of a speed-time graph gets less and less steep, his—-. This does not mean –. It means that –. The force of —. Eventually he travels at a steady, –. The line is horizontal because his speed is –.
A
changes less quickly; that he is slowing down; it takes longer for his speed to increase; air resistance increases until eventually it balances the forward force; terminal velocity; no longer changing
19
Q
If one of the variables in your table is a discrete variable, then you will need to –.
A
plot a bar chart or pie chart
20
Q
The speed of a racing car is a –.
A
continuous variable because it varies all the time
21
Q
On a distance-time graph for a car:
— 3
A
- when the line is horizontal the car is stationary
- a straight sloping line means that the car is moving at a steady speed
- when the line curves up the car is accelerating.
22
Q
On a speed-time graph for a car:
– 2
A
- when the line is horizontal, the car is moving at a steady speed
- a straight sloping line means that the car is accelerating at a steady rate.
23
Q
When both variables are continuous, - are used.
A
line graphs
24
Q
When an object is balanced it behaves as if – When the diver floats, her —.
A
there is no force on it.; weight is balanced by the upthrust of the water
25
If the forces on an object are balanced, its ---:
2
motion will not change
* If it is not moving it will stay still. (stationary)
* If it is moving it will keep moving at a steady speed.
26
If the forces --, they are unbalanced.
If the forces are unbalanced then the --:
2
on an object are not equal and opposite
motion of the object will change
* If it is not moving it will start moving.
* Ifit is moving it will speed up (accelerate), slow down (decelerate), or change direction.
27
If you know the---, you can work out the --, or net force.
size of each force acting on an object; resultant force
28
* If the resultant force is zero the --.
* If the resultant force is not zero the --.
forces are balanced
forces are unbalanced
29
An object can ---. It will move at a steady speed.
move without a resultant force
30
Thought experiement
the process of thinking through what might happen in an experiment without actually doing it
31
All surfaces, even surfaces that feel very smooth, are- .
uneven
32
* If you push a book on a table and it does not move, the forces are -.
* The uneven surfaces produce the ---.
* When your force is bigger than friction, the forces are -.
* Then the book will --.
balanced; force of friction that you have to overcome; unbalanced; accelerate
33
When the force applied is ---, the object will move.
larger than the maximum fraction
34
3 ways to reduce friction
1. Skiers and snowboarders wax their skis.
2. You put oil in a car to reduce friction between engine parts that move. This is called lubrication. Cyclists lubricate the chains of their bicycles.
3. Ball-bearings inside the wheels of a skateboard roll over each other as wheel turns. (slow down surface wear)
35
How does lubrication work?
A layer of oil between two surfaces makes it easier for the surfaces to slide over each other. It reduces the force of friction. There will be less collision of the bumps; the surfaces will slide over each other more easily.
36
3 usefulness of friction
1. Walk:friction acts between your feet and the ground, making it possible for you to move
2. Vehicles:need the force of friction between the tyres and the road to make them move.
3. Bicycles and cars:friction acts between brakes and wheels to stop (brake pads or brake blocks and the wheels)
37
In icy conditions ---. Wheels skid because ---.
friction is reduced; there is not enough friction for them to grip the road
38
You can use -- to measure the --- between two surfaces.
a newtonmeter; force of friction
39
Friction is useful for -----.
grip, to start moving, or for braking
40
A moving object still needs --- in order to keep it moving at a steady speed.
a force to balance the forces slowing it down
41
Aristotle's ideas about motion
objects move only when they are pushed, and slow down when you remove the force. (no friction)
42
A thought experiment is useful to ----.
what might happen in a situation where it is not possible to carry out the experiment
43
In most situations, the force is needed to ---.
Without --, no force is needed to ---.
cancel out friction or air resistance; keep something moving
44
Newton's first law of motion states that, ---
unless an external force is applied, stationary objects will remain stationary, and moving objects will continue to move in a straight line at a steady speed.
45
There is force in the rope that balances the --. The force in a rope that is being --. As you pull on the rope the ---. The tension force that you feel is the force ---.
climber's weight; stretched is called tension; particles inside are moving apart; of attraction pulling the particles back again
46
A bungee cord is made of ---.
lots of elastic cords all bound togethe
47
The tension in the rope --- on the climber.
exerts an upwards force
48
It is important to use the right spring for the job, so you need to find out ---.
how much a spring will stretch when you apply a force to it
49
The bigger the force, the bigger the--; if you double the force you ---. The extension is ---. That is why a newtonmeter contains a spring.
extension; double extension; proportional to the force
50
The upthrust -- so the boat floats.
* -- with the bottom of the boat.
* They ---.
* A large area produces a ---.
balances the weight; Water particles collide; push the boat up; big force that can balance a big weight
50
What causes elasticity?
Internal forces within the material that resist deformation and restore it to its original state.
50
If you keep loading more and more on, eventually the spring---. It has reached its limit, called the --. The spring cannot spring back, and it ---. Elastic material will --.
will not return to its original length when you remove the force; elastic limit; is permanently extended; break if the force applied to them is too big
51
The label of a trampoline says that the weight limit for the trampoline is 1200 N.
The springs must be -- when the weight is 1200.
below their elastic limit
51
An object underwater appears to -- because of the upthrust.
The water level will rise because the --.
An object weigh 10 N, and the weigh of the displaced water is 4N, the ---
weigh less; weight displace some water; apparent weight of the object is now 6N
52
Anomalous results:
2
* should be identified
* should be repeated or checked
52
Results table shows
what you are measuring and the unit
52
Reliable results (2)
* she repeated each measurement three times
* repeated measurements make the data more accurate and reliable
53
A line of best fit ---
goes through most points and is a smooth line or curve
54
Levers work because --
some forces produce a turning effect
54
How to produce a turning force when using a lever
push down on one side
54
A lever works because:
2
* the distance from the effort to the pivot is bigger than the distance from the load to the pivot
* you push down with a force that is much smaller than the weight of the stone to move it.
54
Forces can change the motion of objects, and they can also --. Every time you ---, you are applying a turning force.
make things turn; close a door, use a wheelbarrow, or sit on a see-saw
54
A lever is a bar that --.
* The -- is called the effort.
* The --- is called the load.
* The bar rotates --
can turn when you exert a force on one end; force that you exert on the bar; weight of the object that you lift; about a pivot (fulcrum)
55
3 force multipliers
hammer, wheelbarrow and straight-bar lever
56
what is so special about a wheelbarrow as a lever?
load is between the effort and the pivot.
57
2 distance multipliers
tongs and tweezers
58
Forces can turn an object --.
clockwise or anticlockwise about a pivot
59
what is the use of the pole of a tightrope walker
The pole is used to alter the turning forces/cancels out the turning force to help him balance
60
-- is called a moment.
The size of the moment depends on the ---.
The turning effect of a force; force being applied and how far it is from a pivot
61
Moment=
* Moment (Nm) = force (N) × perpendicular distance from the pivot (m)
* A moment is measured in newton metres (Nm)
62
When two people balance on a see-saw, we say that ---.
This means that the --- are the same.
it is in equilibrium; anticlockwise moments and clockwise moments
63
If you move the centre of the plank ---, there will be a turning point on the plank. The plank's weight ---.
away from the pivot; acts through its centre of mass
64
It is harder to topple objects with a ---.
The object does not need to be -- before the ---.
low centre of mass than objects with a high centre of mass; tipped as far; centre of mass moves outside the pivot
65
The earthmover does not sink because ---.
its weight is spread out over a bigger area
65
Pressure is a measure ---
of the force exerted by an object or substance over a certain area
66
Pressure is measured in ---
newtons per metre squared (N/m^2) or N/cm^2
66
1 N/m^2 is also called ---
1 pascal (Pa)
67
5N/cm^2= N/m^2
50000
68
Useful to increase pressure (6)
blades of knives and scissors (blunt->bigger area->same force is no longer high enough to cut things)
nail (pinted end->The pressure produced on a surface when you hit the nail with the hammer will be very large)
wide flat feet of wading birds and large camel feet (X sink into soft surface : sand and mud)
wide handles and straps (more comfortable)
bike tyres (off-road bikes have wider tyres to travel across mud)
68
football boot and pressure
studs have a smaller area than area of foot -> more pressure -> studs sink into the ground & help footballer to grip the ground and move more easily
69
Liquid pressure is due to the ---.
forces between the liquid particles and the surfaces of a container
70
The particles in a liquid are
very close together, so liquids are --
incompressible
71
When a force is applied to a liquid, the forces ---. To demonstrate that the pressure in a liquid acts in all directions:
* Fill a bag with water and make holes in it.
* When it is squeezed, the water ---.
* The curved path of the water is due to -
between the particles increase, and the forces act in all directions
comes out of the bag at 90° to the surface
gravity.
71
It is liquid pressure that produces ---
upthrust, the force that keeps things afloat.
72
* Liquid pressure at a point depends on ---
* There is-- water above a point at the bottom of a lake than there is half way down.
* The liquid pressure at the bottom of a lake is --
the weight of water above it; twice as much; double the pressure half way down
73
Why is the bottom of a dam wall many times thicker than the top
the pressure at the bottom is much bigger
74
application of the knowledge of liquid pressure
When people go deep underwater they use diving vessels or submarines with very strong walls to withstand the pressure.
75
pressure in liquid or gas is measured with
pressure gauge
This contains a tube that is curled up. The tube straightens out as the pressure inside the tube increases. This moves a needle to show a reading on a scale.
76
In the particle model particles in a gas are ---
far apart, and are moving fast.
77
how is gas pressure produced in terms of gas in a balloon
* Pump air particles into the balloon.
* Particles bump into each other and into the rubber of the balloon.
* The collisions with the walls of the container produce gas pressure
78
What affects gas pressure
more particles added
particles in a smaller volume
particles moving faster (increased temperature)
79
* By blowing more air into the balloon, David ---
* If there are --- the balloon will get bigger.
* When too much gas has been added, the balloon -.
increases the pressure inside it.; more collisions on the inside than on the outside; bursts
79
Gas pressure changes when ----
the number of collisions between gas particles
and the container walls changes
80
The air around us --- on our bodies all the time. This is called --. We do not feel the pressure because ---
exerts gas pressure; atmospheric pressure; it is balanced by the pressure of the gases and liquids in our bodies pushing outwards (exterting a pressure on the walls of their container).
81
The atmospheric pressure at sea level is bigger than the ---
* --- towards the Earth.
* The air near the Earth's surface is -
* If the particles are --, then the pressure is -.
* This means that there will be ---
atmospheric pressure high up a mountain.
Gravity pulls the air particles
compressed.
closer together; bigger
more collisions producing a bigger force and a bigger pressure near the surface.
82
oxygen tanks
- usage
- how it works
- for firefighters and where oxygen levels are low
- gas compressed into a small volume otherwise they would not be able to carry the number of containers of oxygen that they need.
The pressure inside the oxygen tanks is very high.
The tanks are made of metal which can withstand the high pressure.
83
gas pressure is caused===
by particles colliding with the walls of the container
84
Atmospheric pressure decreases as you ---
go up a mountain
