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Mechanics Flashcards

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1
Q

speed

A

rate of change of distance with respect to time (ms^-1)

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2
Q

acceleration

A

rate of change of velocity with respect to time (ms^-2)

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3
Q

displacement

A

distance in a given direction (m)
vector quantity

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4
Q

velocity

A

rate of change of displacement with respect to time (ms^-1)
vector quantity

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5
Q

acceleration due to gravity

A

in the absence of air resistance, all objects near the earth’s surface, if released, will fall downwards with the same acceleration. This is acceleration due to gravity. g=9.8ms^-2

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6
Q

scalar

A

quantity with magnitude but no direction

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6
Q

vector

A

quantity with direction and magnitude (oh yeah!!)

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7
Q

force

A

anything that causes the velocity of an object to change i.e. speed up/slow down.
unit: Newton (N)

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8
Q

mass

A

(m) of a body is a measure of how difficult it is to accelerate that body
unit: kg

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9
Q

average speed

A

distance/time

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10
Q

the newton

A

1N is the force that gives a mass of 1kg an acceleration of 1ms^-1

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11
Q

weight

A

the weight of an object is the force of the earth’s gravity acting on it.
W=mg//F=ma
unit: Newton

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12
Q

momentum

A

ρ = mv
unit: kgms^-1 kilogram metre per second

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13
Q

Newton’s 1st law

A

law of inertia: a body will remain in a state of rest or travelling with a constant velocity unless an external unbalanced force acts on it

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14
Q

newton’s 2nd law

A

F = ma //
when an unbalanced force acts on a body the rate of change of the body’s momentum is directly proportional to the force and takes place in the direction of the force:
F ∝ mv-mu/t

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15
Q

newton’s 3rd law

A

every force has an equal and opposite force. i.e. friction opposes motion

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16
Q

friction

A

force that directly opposes motion in the opposite direction to the motion

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17
Q

principle of the conservation of momentum

A

momentum before = momentum after in a closed system (no external forces).
m1u1 + m2u2 = m1v1 + m2v2

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18
Q

density

A

mass per unit volume;
ρ = m/V
unit: kgm^-3

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19
Q

pressure

A

force per unit area
unit: pascal (Pa) or Nm^-2

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20
Q

pressure in solids

A

P = F/A

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21
Q

pressure in liquids

A

P = ρgh

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22
Q

archimedes’ principle

A

states that when an object is partially/fully immersed in a fluid it experiences an upthrust equal in size to the weight of the fluid displaced

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23
Q

law of flotation

A

states that the weight of a floating object is equal to the weight of the liquid displaced

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24
Q

boyle’s law

A

states that at a constant temperature the volume of a fixed mass of gas is inversely proportional to its pressure
P ∝ 1/V
PV = k

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25
Q

newton’s law of universal gravitation

A

any two point masses in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
F ∝ m1m2/d^2 //
F = Gm1m2/d^2 //
F = GM/d^2

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26
Q

inverse square law

A

an inverse-square law is any scientific law stating that the observed “intensity” of a specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity.

27
Q

moment of a force

A

turning effect of a force
M = Fd
d = distance from fulcrum

28
Q

laws of equilibrium for coplanar forces

A

if a body is in equilibrium then sum of upforces = sum of downforces and sum of CW moments = sum of AC moments

29
Q

lever

A

a rigid body free to rotate around a fixed point called a fulcrum

30
Q

couple

A

2 parallel forces equal in size acting in opposite directions with no common line of action e.g. handlebars

31
Q

work

A

W = Fs
s = displacement
unit: Joule (J) or Nm

32
Q

the joule

A

1J = the amount of work done when a force of 1N acts for a distance in the direction of the force

33
Q

energy (E)

A

the ability to do work
unit: Joule

34
Q

9 types of energy

A
  1. kinetic
  2. potential (gravitational/elastic)
  3. chemical
  4. sound
  5. electrical
  6. nuclear
  7. electromagnetic radiation (light)
  8. internal
  9. heat
35
Q

kinetic energy

A

Ek: the energy a body has due to its motion
Ek = 1/2mv^2

36
Q

potential energy (grav)

A

Ep: the energy a body has due to its position in a force field
Ep = mgh

37
Q

renewable sources of energy

A

wind, solar, hydroelectric, geothermal, nuclear fusion, biomass, tidal

38
Q

power

A

the rate at which work is done/energy is converted from one form to another
P = W/t //
P = E/t
unit: watt (W) or Js^-1

39
Q

power efficiency

A

power output/power input *100

40
Q

principle of the conservation of energy

A

energy can neither be created nor destroyed, it can only be converted from one form to another

41
Q

Torque

A

T = Fd
// moment of a couple

42
Q

terminal velocity

A

where air resistance (friction) is equal and opposite to the weight of the falling object
i.e. falling at constant velocity

43
Q

work

A

when a force moves a body through displacement in the direction of the force
W=Fs
unit: Joule or Nm

44
Q

energy

A

the ability to do work

45
Q

hydrometer

A

based on law of flotation/buoyancy.
1. finding % alcohol
2. density of sulphuric acid in car battery
3. % of fat in milk

46
Q

pressure in a gas

A

increases with depth, acts in all directions

47
Q

atmospheric pressure

A

pressure of earth’s atmosphere acting on any object near the earth
at sea level atm. pressure = 1*10^5Pa = 1 atmosphere. decreases further from sea level you move

48
Q

high pressure weather

A

dry, clear skies, little wind

49
Q

low pressure weather

A

cloudy, wet, windy

50
Q

angle in radians

A

θ = s/r
s = arc length
r = radius

51
Q

constant angular velocity

A

rate of change of angle with respect to time
w = θ/t
unit: rad s^-1

52
Q

centripetal force

A

the force acting towards the centre that is needed to keep an object moving in a circle

53
Q

what does centripetal force depend on

A

-mass of object
-radius of turn
-velocity of object

54
Q

centripetal force eqns

A

F = mv^2/r

F = mrw^2

55
Q

linear tangential velocity

A

at any point on the circle the object has tangential speed (linear) i.e. if you let it go it will move in a straight line
v = rw

56
Q

centripetal acceleration

A

if an object is moving in a circle it has acceleration towards the centre

a = v^2/r

a = rw^2

57
Q

period (T) of an orbit

A

time taken for a satellite to go once around the central body

T = 2πr/v

58
Q

kepler’s 3rd law

A

T^2 = 4π^2R^3/GM

T^2 ∝ R^3
T ∝ 1/√M

59
Q

geostationary orbit

A

remains at rest above the same point on the equator.
-orbits in the equatorial plane
-period is 24 hours
-satellite moves in the same direction as the earth
-height above earth is approx 36,000km

60
Q

Hooke’s law

A

when an object is bent, stretched or compressed by a displacement then the restoring force is directly proportional to the displacement provided the elastic limit is not reached
F = -ks
k = elastic constant

61
Q

restoring force

A

force pulling object back to its original position

62
Q

elastic limit

A

if an object exceeds its elastic limit it becomes permanently strained and will not return to its original shape

63
Q

simple harmonic motion

A

object said to be moving with simple harmonic motion if
-its acceleration is directly proportional to its distance from a fixed point on its path
-its acceleration is always directed towards that point

a = -w^2s
w^2 = constant

64
Q

period of SHM

A

T = 1/f
T = time for total oscillations/number of oscillations

T = 2π/w

65
Q

amplitude

A

greatest displacement the particle has from the equilibrium position

Physics (12 decks)

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