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Flashcards in Mechanics -Terms and definitions Deck (100):
1

Gravitational Acceleration

9.8m/s/s

2

Newton's Second Law of Motion

If acceleration and velocity are in the same direction, the object is accelerating.
If acceleration and velocity are in opposite directions, the object is decelerating.
Where there is an acceleration we use kinematic equations.

3

Elastic and Inelastic Collisions

During a collision, if there is NO loss of kinetic energy, we call it ELASTIC collision.
During a collision, if there IS loss of kinetic energy, we call it INELASTIC collision.
(There will always be some lost due to friction, but if it's a not much then it's inelastic)

Ek=(1/2)mv^2

4

Circular motion equations (5)

Fc=mac
Fc = centripetal force = Newtons = N
m = mass = kg
ac = centripetal acceleration = m/s/s

v=(2πr)/T =2πrF
v = velocity = m/s
π = pie
r = radius
T = period = unit: S
F = frequency = unit: S^-1 or Hertz (Hz)

Fc=(mv^2)/r

c=2πr
c = circumfrence
π = pie
r = radius

ac=(v^2)/r

5

Energy Equations (5)

P=W/t
W=F/d
Ek=(1/2)mv^2
W=Pt
Ep=mgΔh

6

Power

The rate at which energy is transformed (how fast it's transformed).
P=W/t or P=ΔE/t
P = Power -J/s or Watts (W)
W = Work (J)
ΔE = change in energy (J)
t = time (s)

7

Projectile motion horizontal

In the horizontal direction, there is no force acting on the object, so the horizontal velocity will stay the same. (No acceleration).

8

Rounding

To the least accurate amount of significant figures that is given in the question.
Because the end result's accuracy can't be more accurate than the data given itself.
(Round at the end of the question only)

9

Equilibrium

All forces are balanced, no linear acceleration.
Clockwise torque equals to anticlockwise torque, no angular acceleration.

10

Torque

Def: Torque is the turning effect of a force around a pivot point.
Torque is sometimes called 'moment', or 'moment of force'.
symbol: T

11

Momentum

The quantity of motion of a moving body, measured as a product of its mass and velocity.
Used in EXPLOSIONs and COLLISIONs.

"Moving objects resist being stopped, a quality which we call their inertia. We experience a force when struck by a moving object created by a change in momentum."

Momentum is a vector quantity, it has both size and direction. The direction of momentum is the same as the velocity.

12

Elastical Potential Energy

Stretched out string, once you let it go it will contract similar to dropping a ball w gravitational Ep.

Ep=(1/2)kx^2
Ep = Elastic Potential Energy (J)
k = spring constant (N/m)
x = extension (m)

13

Conservation of Momentum

The momentum of a system stays the same if there's no external force acting on it.
This is used in collisions and explosions.

14

Circular Motion

"Newton's first law states that a body will continue at a constant velocity in a straight line unless it is acted on by an external force. The velocity of the spinning object is constantly changing so there must be an external force acting upon it -the centripetal force. Remove the centripetal force and the object flies off at a tangent."

An object rotates around a fixed point with a constant speed and radius.
The direction of the velocity is TANGENTAL (In tangent to the circle)
Even though the SPEED of the object does not change, the direction is constantly changing thus the velocity is constantly changing.

15

Projectile motion vertical

In the vertical direction, the only force that is acting is gravity going down. It is under constant acceleration at 9.8m/s/s

16

ac

centripetal acceleration

17

Period (T)

def: The time that it takes for one revolution (one circle) to occur.
Unit: S

18

Projectile def

A projectile is any object that moves through the air without its own source of power, only under the influence of gravity (air resistance is ignored).

19

Impulse

Change of momentum is caused by a force over a period of time.

ΔP->=Ft
ΔP = kgm/s (the arrow shows the direction of the net impulse).
F = N
t = s

20

Kinematic Equations

Vf=Vi+at
d=Vit+1/2at^2
Vf^2=Vi^2+2ad
d=((Vi+Vf)/2)t

Vi = initial velocity (m/s)
Vf = final velocity (m/s)
t = time (s)
a = acceleration (ms^-2)
d = distance (m)

21

Spring Constant

Represents the stiffness of the spring (the bigger the spring constant the stiffer the spring)

F=kx or F=-kx
F = Force (N)
k = Spring constant (N/m)
x = Extension (m)
(-) = Restoring force in the spring -essentially the force opposing the extension (downwards) force. Don't often need to use.

22

Conservation of Energy

Energy cannot be created or destroyed
In a system that does not undergo any force from outside the system, the amount of energy is constant, irrespective of its changes in form.

23

Fc

Centripetal force

24

Torque Calculations

T=Fd
T = Torque = Newtons per meter = N.m
F = Force = Newtons = N
d = perpendicular distance (from pivot pt.) = meters = m

Tac=Tc
Tac = Sum of Torque anticlockwise
Tc = Sum of Torque clockwise

25

Verticle Motion under Gravity

When an object is under free-fall, provided air resistance can be ignored, its acceleration is due to gravity.

26

Kinetic Energy

Is the energy an object has because of its movement. As an object speeds up it gains kinetic energy, as it slows down it loses it.

Ek=(1/2)mv^2

27

Newton's Third Law of Motion

Every acting force will have an equal and opposite reaction force.

28

Newton's First Law of Motion

If all the forces acting upon an object are balanced, then the object will either stay stationary or travel at a constant speed/velocity.
d=vt
(Acceleration = 0)

If the forces acting upon an object are NOT balanced, then the object will have an acceleration. The direction of the acceleration will be the same as the net force.
a=F/m or F=ma

29

Frequency (F)

def: The number of revolutions that can happen in 1 second.
Unit: S^-1 or Hertz (Hz)

30

Gravitational Energy

When an object is able to gain kinetic energy in the future on account of its position, being raised above the ground.

ΔEp=mgΔh

31

Momentum equations

P=mv
P = momentum = kg.m/s
m = mass = kg
v = velocity = m/s

Ptotal-> = Pa-> + Pb->

32

Work

If a force acting on an object has moved the object in the direction of the force for a distance, then we say the force has DONE WORK.
Work done = energy transformed
thus
when energy is transformed, there must be a force doing work.

W=Fd

33

Accelerate vs acceleration

Accelerate: When something changes its velocity
Acceleration: The rate of change of velocity of a moving object. Can result from a change in speed and/or a change in direction

34

Acceleration due to gravity

On surface of earth, value is 9.8ms^-2
Increases nearer the poles, decreases with altitude and depth inside the earth

35

Average velocity

Total displacement divided by the total time taken

36

Axis

The imaginary line about which a planet or other object rotates

37

Balanced forces

When a number of forces act on a body, and the resultant force is zero

38

Centripetal force

Force required to keep an object moving in a circle

39

Change in momentum

Momentum after minus momentum before

40

Change in velocity

Velocity after minus velocity before

41

Circular motion

The motion of a body along a circular path

42

Circular orbit

An orbit that is circular

43

Collision

Objects hitting eachother

44

Combined mass

Sum of masses involved

45

Conservation of energy

When energy is transformed from one type of energy into another, the total energy before and after are always the same.

46

Conservation of mass

Mass, including single atoms, is neither created or destroyed in a chemical reaction (not measurably anyway!)

47

Conservation of momentum

The total momentum of a group of a closed system remains constant in the absence of external forces

48

Constant speed

Speed that stays the same

49

Deceleration

Negative acceleration

50

Displacement

The change in the position of an object in a particular direction

51

Distance

The actual length of the path traveled by a body irrespective of the direction is called the distance traveled

52

Equations of motion

Set of formulas used to describe motion mathematically

53

Force

Forces change the state of rest or of uniform motion, the direction of motion, or the shape and size of a body

54

Force of gravitation

The force with which two objects attract eachother because of their masses

55

Free fall

The motion of a body towards the earth when no other force except weight acts on it.

56

Friction

The force that resists the motion of one surface relative to another with which it is in contact

57

Gravitational constant G

The universal gravitational constant G which appears in the equation for Newton's law of gravitation

58

Gravity

Forces of attraction between two objects due to their mass

59

Horizontal circle

A circle that involves no gain or loss in gravitational potential energy

60

Impulse

Change in momentum caused by an external force

61

Inelastic collision

Collision where kinetic energy is not conserved (some energy is converted to sound or heat etc.)

62

Inertia

The property of matter that causes it to resist any change in its state of rest or of uniform motion

63

Kinetic energy

Energy possessed by a body by the virtue of its motion

64

Mass

The quantity of matter contained in a body it remains the same everywhere

65

Matter

Anything that occupies space and has mass

66

Momentum

The product of a body's mass and velocity

67

Motion

Manner of how a body moves

68

Net force

The resulting force after all forces have been added using vector

69

Newton

A unit of force defined as 1 Newton force is needed to accelerate a 1kg mass 1 ms^-2

70

Newton's first law of motion

A body continues in a state of rest or of uniform motion in a straight line unless it is acted upon by an external force

71

Newton's law of gravitation

Force between two particles is proportional to their masses and inversely proportional to the square of the distance between them

72

Non Uniform Acceleration

When the velocity of a body increases by unequal intervals of time

73

Non Uniform Speed

When a body travels unequal distances in equal intervals of time

74

Non Uniform Velocity

Covers unequal distances in equal intervals of time in one direction
Covers equal distances in equal intervals but changes direction

75

Origin

Initial position of an object

76

Oscillatory motion

The to and fro motion of a body about its mean position

77

Pendulum

A mass (called "Bob") tied to a piece of string

78

Period

For a particular vibration, the time for one complete oscillation

79

Pivot

Point upon which an object turns or rotates

80

Potential Energy

The energy of a body due to its height or the energy of a body due to its shape

81

Projectile

An object thrown into space either horizontally and under the action of gravity

82

Radius

Distance from centre of circle to edge

83

Range

The horizontal distance traveled by a projectile

84

Rectilinear Motion

The motion of a body in a straight line is called rectilinear motion

85

Retardation

Negative acceleration is called retardation. In retardation the velocity of a body decreases over time

86

Revolution

One full circle 2π

87

Speed

The distance traveled by a body in one unit of time is called its speed

88

Spring Constant

Force required to extend or compress a spring by one metre

89

State of motion

When a body changes its position with respect ot a fixed point

90

State of Rest

When a body does not change its position with respect to a fixed point

91

Tangential velocity

Velocity in a perpendicular direction to the centripetal force at a given instant

92

Tension force

Force in object that opposes them being stretched

93

Time of flight

The time taken by a projectile from the moment it is thrown until it touches the ground

94

Torque

Turning force (not applied through the centre of mass)

95

Unbalanced forces

When a number of forces act on a body and the resultant force is not zero

96

Uniform circular motion

The motion of an object in a circular path with uniform speed

97

Velocity

Distance traveled by a body in a particular direction per unit time

98

Vertical circle

Circular motion where the speed, as well as the direction of the object, is constantly changing

99

Weight

The force with which a body is attracted towards the center of the earth

100

Work

Work is done when force acting on a body moves it