1
Q
Define displacement
A
Displacement is the distance from a reference point in a specified direction.
2
Q
Define velocity.
A
Velocity is the rate of change of displacement.
3
Q
How is instantaneous velocity found from a displacement-time graph?
A
To find instantaneous velocity from a displacement-time graph:
draw a tangent to the curve at the required time
calculate the gradient of the tangent
4
Q
What are the kinematic equations used for?
A
The kinematic equations are used for describing the motion of objects undergoing uniform acceleration.
5
Q
What does the gradient of a displacement-time graph represent?
A
The gradient of a displacement-time graph represents the velocity of the object.
6
Q
What does the area under a velocity-time graph represent?
A
Distance travelled (displacement)
7
Q
What does the gradient of a velocity-time graph represent?
A
The gradient of a velocity-time graph represents the acceleration of the object.
8
Q
What does the area under an acceleration-time graph represent?
A
The area under an acceleration-time graph is equal to the change in velocity.
9
Q
What is a projectile?
A
A projectile is a particle that moves freely under gravity in a two-dimensional plane.
10
Q
Define the maximum height attained by a projectile.
A
The maximum height attained by a projectile is the height at which it is momentarily at rest, where the vertical velocity component equals zero.
11
Q
What is the equation for the vertical component of the velocity of an object in projectile motion.
A
The equation for the vertical component of the velocity of an object in projectile motion is: v subscript y equals u sin theta
Where:
v subscript y = vertical velocity component, measured in metres per second (m s-1)
u = resultant velocity of the projectile, measured in metres per second (m s-1)
theta = angle of the projectile to the horizontal, measured in degrees (degree)
12
Q
What is the equation for the horizontal component of the velocity of an object in projectile motion?
A
The equation for the horizontal component of the velocity of an object in projectile motion is: v subscript x equals u cos theta
Where:
v subscript x = horizontal component of velocity, measured in metres per second (m s-1)
u = resultant velocity of the projectile, measured in metres per second (m s-1)
theta = angle of the projectile to the horizontal, measured in degrees (degree)
13
Q
Define fluid resistance.
A
Fluid resistance is a frictional force that opposes the motion of an object moving through a fluid. Another term for fluid resistance is viscous drag.
14
Q
Name the factors affected by fluid resistance in projectile motion. (5)
A
time of flight
horizontal velocity
horizontal acceleration
range
shape of trajectory (Air resistance changes the shape of the trajectory of a projectile; it is no longer a parabola, and its path is steeper on the way down than it is on the way up.)
15
Q
Explain how an object in free fall reaches terminal speed.
A
initially, weight > viscous drag
resultant force acts downward
object accelerates
viscous drag force increases with speed
eventually viscous drag = weight
resultant force = zero
object no longer accelerates
object falls at a constant terminal speed
16
Q
Explain how a skydiver in free fall at terminal speed achieves a new terminal speed after opening their parachute.
A
viscous drag increases when the parachute opens
viscous drag > weight
resultant force acts upward
object decelerates
viscous drag decreases as speed decreases
eventually viscous drag = weight
resultant force = zero
object no longer accelerates
object falls at a new slower terminal speed
17
Q
Define the term resultant force.
A
A resultant force is the vector sum of all the forces exerted on an object, which describes the combined action of all the forces.
18
Q
Define Newton’s first law of motion.
A
Newton’s first law of motion states that a body will remain at rest or move with constant velocity unless acted on by a resultant force.
19
Q
Define the term translational equilibrium.
A
An object is in translational equilibrium if the vector sum of all the forces acting on it are zero, and therefore there is no resultant force.
20
Q
Define Newton’s second law of motion.
(in terms of acceleration and momentum)
A
Newton’s second law of motion states that the resultant force on an object is directly proportional to its acceleration. F=ma (the equation can only be used when mass is constant)
Newton’s second law, in terms of momentum, states that the resultant force on an object is equal to its rate of change of momentum.
21
Q
True or False?
If no drag forces are present, then the acceleration of a falling object is independent of its mass.
A
True.
If no drag forces are present, then the acceleration of a falling object is independent of its mass. Astronauts on the Moon dropped a feather and a hammer from equal heights and found that they landed at the same time.
22
Q
State Newton’s third law of motion.
A
Newton’s third law states that if one body (Object A) exerts a force on another body (Object B), the second body (Object B) will exert a force on the fist body (Object A) which is equal in magnitude but opposite in direction.
23
Q
action-reaction pair
Name four characteristics of a Newton’s third law force pair.
A
the same type of force
equal in magnitude
opposite in direction
acting on different objects
24
Q
A car drives at a constant velocity on a road.
Name a third law force pair in this situation.
A
normal contact forces due to the car pushing on the road and the road pushing back on the car
weight due to the gravitational pull of the Earth on the car and the gravitational pull of the car on the Earth
25
Define tension force.
Tension is a force that occurs within an object when a pulling force is applied to both ends.
26
What is the normal reaction force?
The normal reaction force is the component of the contact force acting perpendicular to the surface.
Reaction forces act on objects supported by a surface.
27
Define a non-contact force.
A non-contact force is a force which acts at a distance without any physical contact between bodies due to the action of a field.
28
What is the gravitational force?
The gravitational force, or weight, is the attractive force experienced by two objects with mass in a gravitational field
29
What causes surface friction?
Surface friction is caused by imperfections in the surfaces of two objects that rub against one another.
30
Define the term static friction.
Static friction is a type of surface friction that occurs when an object is stationary on a surface.
31
Define the term dynamic friction.
Dynamic friction is a type of surface friction that occurs when an object is moving across a surface.
32
Static friction ... in magnitude until movement begins
Static friction increases in magnitude until movement begins.
33
State Hooke's law.
A material obeys Hooke’s law if the extension of the material is directly proportional to the applied force up to the limit of proportionality.
34
Define the term spring constant.
The spring constant is a measure of a spring's stiffness, a higher value indicates a stiffer spring requiring more force
35
Define the term viscosity.
The viscosity of a fluid is its resistance to movement.
36
How is the rate of flow of a fluid related to its coefficient of viscosity?
The rate of flow of a fluid is inversely proportional to its coefficient of viscosity.
37
What is the viscous drag force dependent on? (in terms of the object moving through the fluid)
The object's speed, volume and shape
38
What is the buoyancy force exerted on a body due to?
The buoyancy force is exerted on a body due to the displacement of the fluid it is immersed in.
39
The terminal velocity of a sphere falling through a fluid is directly proportional to...
The terminal velocity of a sphere falling through a fluid is directly proportional to the square of the radius of the sphere.
40
The terminal velocity of a sphere falling through a fluid is indirectly proportional to...
The terminal velocity of a sphere falling through a fluid is indirectly proportional to the viscosity of the fluid.
41
Define linear momentum.
Linear momentum is the momentum of an object that is moving in only one dimension.
42
State the principle of linear momentum.
The principle of linear momentum states that the total linear momentum before a collision is equal to the total linear momentum after a collision. Unless the system is acted on by a resultant external force.
43
Define impulse.
Impulse is when an external resultant force acts on an object for a very short time and changes the object's motion.
44
How is impulse related to momentum
Impulse is equal to change in momentum. Therefore, change in momentum can be used to indirectly measure impulse.
45
How does increasing the time over which a change in momentum occurs change the force experienced by the object.
Increasing the time over which a change in momentum occurs reduces the force experienced by the object.
46
What is the area under a force-time graph?
The area under a force-time graph is impulse
47
Define the term collision.
A collision is when two or more moving objects come together and exert a force on one another for a relatively short time. Momentum is conserved.
48
Define the term explosion.
An explosion is when two or more objects that are initially at rest, are propelled apart from one another. Momentum is conserved.
49
Where do perfectly elastic collisions occur?
Perfectly elastic collisions only occur between particles. However, the theoretical idea of an elastic collision can be used in exam questions.
50
How do you determine if a collision is elastic or inelastic?
To determine whether a collision is elastic or inelastic, compare the kinetic energy before and after the collision. If kinetic energy is conserved, then the collision is elastic.
51
What happens in a totally inelastic collision?
A totally inelastic collision is a special case of an inelastic collision where the colliding bodies stick together and move as one body.
52
Define angular displacement.
Angular displacement is the change in angle, in radians, of a body as it rotates around a circle.
53
Define the term centripetal force.
Centripetal force is defined as the resultant force required to keep a body in a uniform circular motion that acts towards the centre of the circle, perpendicular to the velocity.
54
State the centripetal force for the Earth orbiting the Sun.
The centripetal force for the Earth orbiting the Sun is the gravitational force.
55
State the centripetal force for a ball on a rope moving in a circle.
The centripetal force for a ball on a rope moving in a circle is tension.
56
State the centripetal force for a car going around a circular track.
The centripetal force for a car going around a circular track is friction.
57
True or False?
For an object in circular motion, there is no work done.
True.
For an object in circular motion, there is no work done because there is no change in kinetic energy.
58
Define non-uniform circular motion.
Non-uniform circular motion occurs when there is a changing resultant force on an object in circular motion, such as when an object moves in a vertical circle.
59
True or False?
For a ball on a string swinging in a vertical circle, the direction of the tension force will change continually.
True.
For a ball on a string swinging in a vertical circle, the direction of the tension force will change continually. This is because tension is the centripetal force and is always directed to the centre of the circle.
59
True or False?
For a ball on a string swinging in a vertical circle, the tension force of the string on the ball is greater at the top of the circle than at the bottom.
False.
For a ball on a string swinging in a vertical circle, the tension force of the string on the ball is greater at the bottom of the circle than at the top. This is because the tension has to overcome the weight force at the bottom of the circle.
60
True or False?
For a ball on a string swinging in a vertical circle, the magnitude of the tension force will be constant.
False.
For a ball on a string swinging in a vertical circle, the magnitude of the tension force will change continuously. This is because tension is the centripetal force, which is greater at the bottom because it also has to overcome the weight force at the bottom of the circle.
61
For an object in non-uniform circular motion, when in the circle is the centripetal force at a maximum and a minimum?
For an object in non-uniform circular motion, the centripetal force is at a maximum at the bottom of the circle and a minimum at the top of the circle.
62
True or False?
For a ball on a string swinging in a vertical circle, the speed of the ball will be slower at the bottom of the circle than at the top.
False.
For a ball on a string swinging in a vertical circle, the speed of the ball will be faster at the bottom of the circle than at the top, because the acceleration is greater at the bottom.
63
State the three energy types that are considered mechanical energy types.
kinetic
gravitational potential
elastic potential
64
Define the term dissipated energy
The term dissipated energy means wasted energy transferred to the surroundings that cannot easily be used for another purpose. Energy is usually dissipated as heat, light and sound.
65
Define Work Done.
Work is done when a force is applied to an object and results in the object's movement over a distance in the direction of the force.
It is equivalent to energy transferred and measure in Nm or J
66
Define kinetic energy.
Kinetic energy is the energy an object has due to its translational motion.
67
Define elastic potential energy.
Elastic potential energy is defined as the energy stored within a material when it is stretched or compressed.
68
Why is it dangerous when a wire under stress suddenly breaks?
It is dangerous when a wire under stress suddenly breaks because the elastic potential energy stored in the strained wire is converted into kinetic energy. The greater the extension of a wire, the greater the speed it will have when it breaks.
69
Define a non-conservative force.
A non-conservative force is one that dissipates energy away from the system.
70
Define Power.
Power is the rate at which energy is transferred.
71
What is a fuel?
A fuel is anything that can be burned to produce heat, which can be used for an engine to work.
72
Define energy density.
Energy density is the amount of energy that a fuel can provide per unit volume of fuel.
73
What is one litre (1 L) in cubic metres (m^3)?
1L = 0.001m^3
74
Define a moment.
A moment is the product of a force and the perpendicular distance from a pivot.
It describes the turning effect of a force around a particular point, usually when the rotation is incomplete.
75
Define a couple.
A couple is a pair of forces which are equal in size and act parallel to each other but in opposite directions and along different lines of action on either side of the axis of rotation. A couple produces a turning effect called torque.
76
What is torque?
Torque is the product of a force and the perpendicular distance from the axis of rotation to its line of action.
It describes the turning effect of a force around an axis of rotation.
77
What are the properties of the forces that act in a couple?
Forces that act in a couple are:
equal in size
opposite in direction
perpendicular to the distance between them
78
What effect does the angle, between the force and the axis of rotation have on the resultant torque?
The effect of angle on the resultant torque is:
when the angle is 90° (perpendicular to the axis of rotation), the resultant torque is at a maximum
as the angle decreases, torque decreases
when the angle is 0° (parallel to the axis of rotation), the resultant torque is zero
79
Define the principle of moments.
The principle of moments states that a body is in rotational equilibrium if the sum of the clockwise moments (torques) is equal to the sum of the anticlockwise moments (torques).
80
What is the condition for a beam to be in rotational equilibrium?
If a beam is in rotational equilibrium: total clockwise torque = total anticlockwise torque.
81
Define unbalanced torque.
Unbalanced torque is when the net resultant torque is not zero, causing angular acceleration.
82
Define angular velocity.
Angular velocity is the rate of change in angular displacement with respect to time. (rad s^-1)
83
Define inertia.
Inertia is the resistance to a change of motion or linear acceleration.
84
True or False?
A larger mass results in greater inertia.
True.
The larger the mass an object has, the greater its inertia.
85
Define the term moment of inertia.
The moment of inertia is the resistance to a change of rotational motion. It depends on the distribution of mass around a chosen axis of rotation. (measured in kg m^2)
86
What factors affect the moment of inertia of an object?
shape
density
orientation relative to the axis of rotation
87
Define Newton's second law for rotation.
Newton's second law for rotation states that the torque required to give a rotating object a certain angular acceleration depends on its moment of inertia.
88
What is the equivalent rotational variable for mass, m?
The equivalent rotational variable for mass, m is the moment of inertia, I.
90
What two variables are proportional to each other in Newton's second law for rotational motion?
net torque and angular acceleration
91
What is angular momentum?
Angular momentum is the product of the moment of inertia and angular velocity of a body. (L)
92
What does conservation of angular momentum mean?
The conservation of angular momentum means that the total angular momentum of a system remains constant unless acted on by a net external torque.
93
Which factors affect the angular momentum of a system?
moment of inertia
angular velocity
94
What is angular impulse?
Angular impulse is the change in angular momentum produced by a torque acting over a time interval.
95
What does the area under a torque-time graph represent?
The area under a torque-time graph is equal to the angular impulse or the change in angular momentum. (kg m^2 s^-1 or N m s)
96
What is rotational kinetic energy?
Rotational kinetic energy is the energy a rotating object possesses due to its angular velocity.
97
What does it mean when an object rolls without slipping?
Rolling without slipping is when an object rolls such that its point of contact with the surface has zero velocity relative to the surface.
98
What is the total kinetic energy of a rolling object?
The total kinetic energy of a rolling object is the sum of its translational and rotational kinetic energy.
99
How is the flight of a ball thrown vertically upwards affected by air resistance?
On the way up, the downwards acceleration is greater than 9.8 because of drag.
At the maximum the instantaeous velocity is zero so no drag.
On the way down, the downwards acceleration is less than 9.8 as drag opposes gravity.
Overall the ball will have a lower max height, a shorter flight time, and a slower final velocity.
100
What is stress?
Stress is the force applied to a cross-sectional area of the material.
101
What is the fracture or breaking point?
The point at which the material breaks completely.
102
What is breaking stress?
The amount of stress required to get to the fracture or breaking point, the maximum amount of stress that can be applied. This means that a material with a high breaking stress can also be described as ductile.
103
What are the units for energy density?
J m^-3
104
What are the units for specific energy?
J Kg^-1
105
True or False?
No work is done by an object in circular motion.
True.
In circular motion, the centripetal force acts towards the center of its trajectory whilst its displacement is perpendicular to this. this means there is no work done for an object moving in circular motion.
106
What is a reference frame?
A reference frame is a set of coordinates to record the position and time of events.
107
In its own reference frame, how is an object considered?
An object is considered stationary in its own reference frame.
(Regardless of whether it is moving relative to another frame.)
108
Define inertial reference frame.
The frame that is non-accelerating meaning it is either at rest or moving with a constant velocity.
109
True or False?
All inertial reference frames are moving at a constant velocity with respect to each other.
True.
All inertial reference frames are moving at a constant velocity with respect to each other.
110
Define the term Galilean relativity.
Galilean relativity is when Newton's laws of motion are the same in all inertial reference frames.
111
How do the laws of physics apply in Galilean relativity?
In galilean relativity, the same laws of physics apply, regardless of the frame of reference, as long as the reference frame is moving in a straight line at a constant velocity.
112
True or False?
In Galilean relativity, an object moving with a constant velocity in one reference frame will have a constant velocity in another reference frame.
True.
In Galilean relativity, an object moving with a constant velocity in one reference frame will have a constant velocity in another reference frame.
However, the magnitude of its velocity will be different.
113
State Einstein's two postulates of special relativity.
Einstein's two postulates of special relativity are:
the laws of physics are the same in all inertial reference frames
the speed of light in a vacuum is the same in all inertial reference frames
114
What is the condition for special relativity to apply?
Special relativity applies when objects are travelling close to the speed of light when time and space are also relative to the frame of reference.
115
True or False?
Velocity addition only works at speeds much lower than the speed of light.
True.
Velocity addition, or the Galilean transformation for the velocity of an object moving within the moving reference frame, only works at speeds much lower than the speed of light.
116
True or False?
Galilean transformations predict that objects can travel faster than the speed of light.
True.
Galilean transformations predict that objects can travel faster than the speed of light, but this cannot be the case, so for objects travelling at speeds close to the speed of light, Lorentz transformations must be used to correct this.
117
What are the Lorentz transformations?
The Lorentz transformations are corrections to the Galilean transformations used when objects are travelling close to the speed of light.
118
What will the Lorentz factor for any moving object be?
It will always be greater than 1.
This is because the speed of any moving object will always be less than the speed of light.
119
When should the Lorentz velocity addition transformations be used?
The Lorentz velocity addition transformations should be used when
an object is moving
both the object and the moving reference frame are travelling close to the speed of light
120
Define the term invariant quantity.
Invariant quantities are quantities that are the same in all reference frames.
121
Name the invariant quantities.
Proper time
Proper length
Space-time interval
Speed of light in a vacuum
122
Define the space-time interval
The space-time interval is the change in space-time between two events as represented on a four-dimensional coordinate system (x,y,z,t) in special relativity.
The space-time interval is an invariant quantity that is the same in all inertial reference frames.
123
Define proper length.
Proper length is the length of an object measured in a reference frame where the object is at rest relative to the observer.
124
Define proper time.
Proper time is the time interval between two events measured in the reference frame where the events occur in the same place.
Proper time is measured by an observer within their own rest frame.
125
What are the units for the space-time interval?
meters
126
Define time dilation
Time dilation is the apparent slowing of time for an object moving at close to the speed of light as measured by a stationary observer.
127
True or False?
For a spaceship travelling at close to the speed of light, time slows down on Earth from the reference frame of the spaceship.
True.
For a spaceship travelling at close to the speed of light, time slows down on Earth from the reference frame of the spaceship because the spaceship is stationary in its own reference frame and Earth is moving at close to the speed of light relative to them.
128
Define length contraction.
Length contraction is the apparent shortening of the length of an object moving at close to the speed of light as measured by a stationary observer.
129
True or False?
Length measurements in length contraction calculations are assumed to be taken at the same time in each reference frame.
True.
Length measurements in length contraction calculations are assumed to be taken at the same time in each reference frame.
130
Define the term relativity of simultaneity.
Relativity of simultaneity refers to the fact that two spatially simultaneous events do not necessarily occur at the same time, depending on the observer's reference frame.
131
True or False?
According to special relativity, two events that occur simultaneously in one reference frame may not occur simultaneously in another reference frame.
True.
According to special relativity, two events that occur simultaneously in one reference frame may not occur simultaneously in another reference frame. This is also referred to as the relativity of simultaneity.
132
True or False?
In Galilean relativity, simultaneity is absolute.
True.
In Galilean relativity, simultaneity is absolute.
If two events occur at the same time in one reference frame, then they also occur at the same time in other reference frames.
133
What are the dimensions of both space and time on a spacetime diagram?
Both have units of meters.
134
What is the time axis labelled as on a spacetime diagram?
ct
135
What is the name of a line on a spacetime diagram?
A line on a spacetime diagram is known as a world line.
136
On a spacetime diagram, what does a steeper gradient mean?
The steeper the gradient, the slower the motion of the object through spacetime.
The gradient of a world line represents the velocity of the object.
137
What world lines are not permitted on spacetime diagrams?
Any gradient shallower than 1 is not possible.
This is because the fastest an object can travel is the speed of light, v = c. At this speed the worldline is at a 45 degree angle from the axes.
138
What are the four relativistic phenomena that can be shown on a spacetime diagram?
multiple reference frames
simultaneity
time dilation
length contraction
139
Which experiment provides evidence for time dilation and length contraction?
The muon lifetime experiment.
140
In the muon lifetime experiment who measures proper time and who measures proper length?
The muon measures proper time and the observer on earth measures proper length.
141
Muons are produced...
in the upper atmosphere as a result of pion decays produced by cosmic rays.
142
At what speed do Muons travel?
0.98c
143
What is the average lifetime of a muon?
2.2 micro s
physics ib
flashcards
Decks in class (5)
# Cards
