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A-Level Physics > 4: Mechanics & Materials > Flashcards

4: Mechanics & Materials Flashcards

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1
Q

Scalar Quantity

A

A quantity with only magnitude

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2
Q

Vector Quantity

A

A quantity with magnitude and direction

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3
Q

Vector Examples (4)

A
  • Velocity
  • Force / Weight
  • Acceleration
  • Displacement
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4
Q

Scalar Examples (3)

A
  • Speed
  • Mass
  • Distance
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5
Q

Addition of Vectors

A

Combining two vectors by calculation (for right angles) or scale drawings (any angles)

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6
Q

Resolution of Vectors

A

Splitting vectors into two component vectors at right angles to each other (e.g., forces along and perpendicular to an inclined plane)

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7
Q

Moment

A

Force x perpendicular distance from the pivot to the line of action of the force

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8
Q

DELETE

A

moment = F d
F is force in N
d is perpendicular distance from the pivot to the line of action of the force in m

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9
Q

Couple

A

A pair of equal and opposite coplanar forces

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10
Q

Principle of Moments

A

An object is at equilibrium if the total anticlockwise moment acting about any point / axis of the object is equal to the total clockwise moment acting about that point / axis

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11
Q

Centre of Mass (2)

A
  • The point, through which the line of action of a force causes no rotation
  • Where the mass of the body can be considered to be concentrated
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12
Q

The Centre of Mass is at the Centre of a _____

A

Uniform regular solid

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13
Q

Displacement

A

The distance an object has travelled from its starting point in a given direction

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14
Q

Speed

A

How fast an object is moving, regardless of direction

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15
Q

Velocity

A

The rate of change of an object’s displacement (speed in a given direction)

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16
Q

Acceleration

A

The rate of change of velocity

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17
Q

Velocity Formula

A

v = Δs / Δt
v is velocity in ms⁻¹
Δs is change in displacement in m
Δt is change in time in s

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18
Q

Acceleration Formula

A

a = Δv / Δt
a is acceleration in ms⁻²
Δv is change in velocity in ms⁻¹
Δt is change in time in s

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19
Q

Area & Gradient of Velocity-Time Graph

A

Area: Change in displacement
Gradient: Acceleration

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20
Q

Gradient of Displacement-Time Graph

A

Velocity

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21
Q

Area of Acceleration-Time Graph

A

Change in velocity

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22
Q

Constants in Equations for Uniform Acceleration (5)

A
  • s is displacement in m
  • u is initial velocity in m s⁻¹
  • v is final velocity in m s⁻¹
  • a is acceleration m s⁻²
  • t is time in s
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23
Q

Define g

A

Acceleration due to gravity

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24
Q

Projectile Motion in Horizontal Direction

A

Projectile travels at constant velocity: there is no resultant force acting on it

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25
Q

Projectile Motion in Vertical Direction

A

There is a resultant force acting downwards on the projectile due to gravity. The projectile has an initial velocity so decelerates upwards until it reaches maximum displacement with velocity 0 (vertex of parabola). Then, it accelerates downwards

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26
Q

Friction

A

A frictional force that acts in the opposite direction to the motion of an object. It occurs between solid surfaces and converts kinetic energy to heat

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27
Q

Drag (3)

A
  • A frictional force that acts in the opposite direction to the motion of an object through a fluid
  • It depends on the viscosity of the fluid and the shape of the object
  • The force increases with speed and converts kinetic energy to heat
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28
Q

Lift (3)

A
  • An upward force on an object moving through a fluid
  • It happens when the shape of an object causes the fluid flowing over it to change direction
  • The force acts perpendicular to the direction in which the fluid is flowing
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29
Q

Terminal Speed (3)

A
  • An object accelerates uniformly from rest using a constant driving force
  • As speed increases, frictional forces increase, reducing the resultant force
  • Eventually, all forces are balanced so the object travels at a maximum, constant velocity
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30
Q

Air Resistance Increases with ____

A

Speed

31
Q

Effect of Air Resistance on Trajectory of a Projectile

A

Cause a deceleration in the horizontal direction. It increases the deceleration in the vertical direction when the projectile travels upwards but reduces the projectile’s downward acceleration. Thus, it reduces the horizontal and vertical displacements of the projectile

32
Q

Factors Affecting Maximum Speed of Vehicle (2)

A
  • Increasing driving force increases maximum speed
  • Increasing frictional forces reduces maximum speed
33
Q

Newton’s 1st Law of Motion

A

The velocity of an object will not change unless a resultant force acts on it

34
Q

Newton’s 2nd Law of Motion

A

The acceleration of an object is proportional to the resultant force acting on it

35
Q

Newton’s 3rd Law of Motion

A

If an object A exerts a force on object B, then object B exerts a force of equal magnitude but opposite direction on object A

36
Q

Force Equation

A

F = m a = Δ(m v) / Δt
F is force in N
m is mass in kg
a is acceleration in ms⁻²
Δ(mv) is change in momentum in kg m s⁻¹
Δt is change in time in s

37
Q

momentum = ____

A

mass x velocity

38
Q

Principle of Linear Momentum

A

Assuming no external forces act, linear momentum is conserved (e.g., collisions & explosions)

39
Q

Force is Rate of ____

A

Change of momentum

40
Q

Impulse

A

Change in momentum

41
Q

Area of Force-Time Graph

A

Impulse

42
Q

Elastic Collision

A

Collisions where both momentum and kinetic energy are conserved

43
Q

Inelastic Collision

A

Collisions where momentum is conserved but kinetic energy isn’t

44
Q

Work Equation

A

W = F s cos θ
W is work done in J
F is force in N
s is displacement in m
θ is angle at which the force acts from the direction of motion

45
Q

Work Done is ____

A

Energy transferred

46
Q

Rate of Doing Work = ____

A

Rate of energy transfer

47
Q

Power Equation

A

P = ΔW / Δt = F v
P is power in W
ΔW is work done in J
Δt is change in time in s
F is force in N
v is velocity in m s⁻¹

48
Q

Area under a Force-Displacement Graph

A

Work done

49
Q

Efficiency Equation

A

efficiency = useful power output / input power

50
Q

Principle of Conservation of Energy

A

The amount of energy in a closed system will not change

51
Q

Gravitational Potential Energy Equation

A

ΔE_p = m g Δh
ΔE_p is change in gravitational potential energy in J
m is mass in kg
g is gravitational field strength in N kg⁻¹
Δh is change in height in m

52
Q

Kinetic Energy Equation

A

E_k = ½ m v²
E_k is kinetic energy in J
m is mass in kg
v is velocity in m s⁻¹

53
Q

Density

A

The mass per unit volume of a material

54
Q

Density Equation

A

ρ = m / V
ρ is density in kg m⁻³
m is mass in kg
V is volume in m³

55
Q

Hooke’s Law

A

The extension of a stretched wire is proportional to the load or force

56
Q

Hooke’s Law Equation

A

F = k ΔL
F is force in N
k is stiffness and spring constant in N m⁻¹
ΔL is extension in m

57
Q

Limit of Proportionality

A

The point, beyond which a material no longer obeys Hooke’s law – where force is no longer proportional to extension

58
Q

Elastic Limit

A

The point, after which the material is permanently stretched

59
Q

Elastic Strain Energy

A

The potential energy stored in a material from the work done deforming the material elastically

60
Q

Energy Stored Equation

A

E = ½ F ΔL
E is energy stored in J
F is force in N
ΔL is extension in m

61
Q

Energy Stored =

A

Area under a force-extension graph

62
Q

Tensile Stress

A

The force applied divided by the cross-sectional area

63
Q

Tensile Strain

A

The change in length divided by the original length of the material

64
Q

Tensile Stress Equation

A

tensile stress = F / A
tensile stress in Pa
F is force in N
A is area in m²

65
Q

Tensile Strain Equation

A

tensile strain = ΔL / L
tensile strain is a ratio
ΔL is extension in m
L is original length in m

66
Q

Breaking Stress

A

The tensile stress that breaks a material

67
Q

Young Modulus Equation

A

Young modulus = tensile stress / tensile strain = F L / A ΔL
Young modulus in Pa
tensile stress in Pa
tensile strain is a ratio
F is force in N
L is original length in m
A is cross-sectional area in m²
ΔL is extension in m

68
Q

Plastic Behaviour

A

Where a material is permanently stretched and doesn’t return to its original shape (when the deforming force is removed). A metal stretched past its elastic limit deforms plastically

69
Q

Brittle Behaviour

A

When a material obeys Hooke’s law until it breaks – it doesn’t deform plastically

70
Q

Conservation of Energy in Vertical Springs (3)

A
  • When a vertical spring suspending a mass is stretched, elastic strain energy is stored in the spring
  • When the end is released, the elastic strain energy is transferred to kinetic energy (as the spring contracts) and gravitational potential energy (as the mass gains height)
  • Then, the spring compresses and kinetic energy is transferred back to elastic strain energy and gravitational potential energy
71
Q

Required Practical 3

A

Determination of g by a freefall method

72
Q

Required Practical 3 Method (6)

A

https://docs.google.com/document/d/1hRsKv6saq_Kb4k5UDMCJaJ3lZKGEnrWiD0Gs-qRB3aQ/edit?usp=sharing
1. Measure the mass of the system
2. Place all the masses on top of the trolley
3. Incline the slope such that the trolley (and all of the masses, which you intend to use to accelerate it) is at rest on the slope and if given a small push, it travels at constant velocity
4. Whilst holding the trolley, attach a known mass from the top of the trolley to the hook
5. Release the trolley and record the acceleration shown by the light gate
6. Repeat steps 5 to 6, incrementing the accelerating masses

73
Q

Required Practical 4

A

Determination of the Young modulus by a simple method

74
Q

Required Practical 4 Method (7)

A

https://docs.google.com/document/d/1rbEfdTEdAUt8Vmx3ArXusU4Rd70gfD2SDuphuv_dsdw/edit?usp=sharing
1. Set up the apparatus as shown in the diagram
2. Measure the diameter and original length of the wire
3. Add a 10 g mass onto the hook
4. Measure the new length of the wire
5. Remove the mass the hook and ensure that the wire returns to its original length
6. If it doesn’t then stop the experiment and discard the last result
7. Otherwise, repeat steps 4 to 6, incrementing the mass on the hook

A-Level Physics (9 decks)

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