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mdcat > NUMS physics > Flashcards

NUMS physics Flashcards

1
Q

displacement + formula

A

displacement: straight-line distance b/w your starting point and your ending point

  • change in position of an object
  • is a vector quantity

displacement = final position - initial position

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2
Q

scalar vs vector quantity

A

scalar: only have magnitude

vector: have both magnitude AND direction

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3
Q

Displacement-Time Graph

A

Slope: Represents velocity

Straight Line: Constant velocity (no acceleration)

Curved Line: Changing velocity (acceleration).

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4
Q

Velocity-Time Graph

A

Slope: Represents acceleration

Area Under the Curve: Represents displacement

Horizontal Line: Constant velocity (zero acceleration)

Sloping Line: Constant acceleration.

Curve: Changing acceleration.

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5
Q

Acceleration-Time Graph

A

Horizontal Line: Constant acceleration.

Area Under the Curve: Represents change in velocity.

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6
Q

Force vs. Acceleration Graph (for Newton’s Second Law)

A

Slope: Represents mass (F = m⋅a)

Straight Line: Indicates that force and acceleration are directly proportional (with mass as the constant).

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7
Q

Deleted

A
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8
Q

Projectile Motion Graphs

A

Trajectory (Position) Graph: Parabolic curve representing the path of a projectile.

Horizontal Distance vs. Time: straight line indicating constant horizontal velocity.

Vertical Distance vs. Time: Parabolic curve showing vertical displacement over time.

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9
Q

Force vs. Time Graph

A

The area under the curve represents impulse, which is equal to the change in momentum.

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10
Q

velocity + formula

A

the speed of something in a specific direction

  • speed doesn’t include direction but velocity does

velocity = displacement/time

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11
Q

acceleration + formula

A

rate at which velocity changes

If you’re speeding up, slowing down, or changing direction, you’re accelerating

  • when an object moves in a circular path at a constant speed, it is still accelerating, because the direction of its velocity is changing

acceleration = change in velocity/time

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12
Q

newton’s 3 laws of motion

A

First Law (Law of Inertia): An object will stay at rest or keep moving in a straight line at constant speed unless acted upon by an external force.

Second Law: The force acting on an object is equal to the mass of that object multiplied by its acceleration.
Formula:
F = m⋅a
F = force, m = mass, and, a = acceleration

Third Law: For every action, there’s an equal and opposite reaction. If you push something, it pushes back with the same force.

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13
Q

linear momentum + formula

A

product of an object’s mass and velocity
- tells you how much motion an object has

p = m⋅v

p= momentum, m = mass, v = velocity

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14
Q

law of conservation of momentum

A

In a closed system (no external forces), the total momentum before an event (like a collision) is equal to the total momentum after the event

TotalMomentumBefore = TotalMomentumAfter

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15
Q

Collisions + 2 types

A

elastic collision: both momentum and kinetic energy are conserved

inelastic collision: momentum is conserved, but kinetic energy is not

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16
Q

at what point during the motion of a projectile is its vertical component of velocity zero?

A

highest point

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17
Q

power is the product of

A

force and velocity

power: rate at which work is done

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18
Q

the area under force-displacement graph gives

A

work

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19
Q

joule’s law

A

relates amount of heat produced by an electric current flowing through a conductor

  • so if you a have a heater, the more electric current flowing through and the more resistant the heater material is and if its on for a long period of time, the more heat it will produce

formula: Q = I^2 Rt

Q = heat produced
I = current
R = resistance
t = time

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20
Q

convex vs concave lens

A

convex lens (converging lens: bends (refracts) light rays inward, focusing them to a point
- lens is thicker in the middle and thinner at the edges
- ex. magnifying glass or the lens in eye

concave lens (diverging lens): spread light rays outward, making them diverge as they pass through
- thinner in the middle and thicker at the edges
- ex. lens used in some glasses for people who are nearsighted

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21
Q

crest & trough of a wave acts as what types of lens

A

crest (highest point of a wave) = convex lens (focuses light rays inward)

trough (lowest point of a wave) = concave lens (focuses light rays outward)

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22
Q

speed of sound at 0ºC and for each degree increase

A

speed of sound at 0ºC: 331.5 m/s

on avg. for each ºC increase in temp above 0ºC, speed of sound in air increases by about 0.61 m/s

  • this is because warmer air has molecules that move faster, allowing sound waves to travel more quickly, increasing the speed of sound at higher temps
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23
Q

isobaric, isochoric, isothermal, adiabatic process

A

isobaric: pressure kept constant, while other variables like volume and temp may change

isochoric: volume kept constant, and no work is done by the gas

adiabatic: no heat exchanged with surroundings, meaning all energy changes result in changes to the internal energy of the system

isothermal: temp kept constant, meaning internal energy of the system remains the same

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24
Q

ohm’s law + formula

A

formula: V = I x R

V = voltage
I = current
R = resistance

states that current though conductor b/w 2 points is directly proportional to voltage across the 2 points and inversely proportional to the resistance as long as temp of conductor is kept constant

so: If you increase the voltage in a circuit, more current will flow. But if you increase the resistance, the current will decrease.

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25
Q

1st, 2nd, & 3rd law of thermodynamics

A
  1. energy cannot be created or destroyed
  2. for a spontaneous process, the entropy of the universe increases
  3. a perfect crystal at zero Kelvin has zero entropy
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26
Q

ampere’s law

A

states that magnetic field (B) around a closed loop is proportional to the current (I) passing through the loop

in simple terms: if you have a wire carrying an electric current, it creates a magnetic field around it. strength of that magnetic field depends on the amount of current flowing through the wire

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27
Q

gauss’s law

A

The electric field around a charged object is related to the total charge inside an imaginary surface around it. If you know the charge inside, you can figure out how strong the electric field is.

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28
Q

electric field intensity + units

A

Electric Field Intensity (E): a measure of the strength of an electric field at any point

formula: E= F/q
q - charge
F - force
​
defined as force per unit charge

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29
Q

gravitational field strength is defined as

A

force per unit mass

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30
Q

relationship b/w resistance of pure metals and temperature

A

the resistance of pure metal increases with an increase in temperature

  • b/c in pure metals, as temp increases, atoms in metal vibrate more and increased vibration causes more collisions b/w free electrons, increasing resistance
  • increase in pressure can also increase resistance, but effect is less pronounced than that of temp
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31
Q

magnetic field inside & outside current carrying wire

A
  • at very center of wire (r=0), magnetic field is 0
  • as you move away from the center of the wire (increasing r), magnetic field increases because enclosed current is increasing
  • field increases linearly with r until you reach the surface of the wire

so: magnetic field inside current carrying wire varies directly with r

outside the wire: magnetic field decreases as you move farther with distance, (inversely proportional to r - 1/r)

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32
Q

when is magnetic flux maximum?

A

when angle b/w magnetic field and vector area is 0º

  • at 90º, magnetic field lines are parallel to the surface, not passing through it, but at 0º, they are perfectly perpendicular and passing through

has something to do with the equation of magnetic flux which is B x A x cos(º)
and like cos (0) =1, but cos(90) = 0

33
Q

momentum

A
  • is a vector quantity
  • units of momentum is N⋅s (SI unit is kg⋅m/s)
  • product of mass and velocity

p = mv

34
Q

slope of displacement-time graph & slope of distance-time graph

A

slope of displacement-time graph: velocity

slope of distance-time graph: speed

35
Q

how to solve this question:

two stones, 10kg and 50kg fall through 80m high cliff. which stone has greater velocity at the bottom? (ignoring air resistance)

A

for objects that free fall under the influence of gravity alone (ignoring air resistance), they accelerate at the same rate which is acceleration due to gravity (g≈ 9.8m/s^2)

  • so, mass does not matter, only height

answer: both of these have the same velocity

36
Q

how to solve this question:

when the speed of your car is halved, by what factor does its kinetic energy decrease?

A

decreases by a factor of 4 or (1/4)

because KE = 1/2mv^2

kinetic energy is proportional to the square of velocity

37
Q

relationship between degree and radian

A

1 radian = 57.3º
1 degree = 0.0175 radian

38
Q

formula for angular displacement

A

θ = s/r

s = arc length (distance covered along the circumference)
r = radius of the circle

39
Q

relationship b/w angular and linear velocity is

A

v = rω

ω = angular velocity
v = linear velocity

40
Q

how to solve this question:

to make frequency of spring oscillation 4 times, what do you do to the mass?

A

frequency of spring oscillation is inversely proportional to the square root of the mass

f∝ 1/√ m

so to increase frequency by a factor of 4, you need to decrease mass by a factor of 4^2 = 16

41
Q

Cp - Cv = R

A

Cp: amount of heat needed to raise the temperature of 1 mole of gas by 1°C at constant pressure

Cv: amount of heat needed to raise the temperature of 1 mole of gas by 1°C at constant volume

Since R is a positive number, Cp must be greater than Cv for the equation to work

Cp > Cv

42
Q

capacitance (+ what it depends on)

A

capacitance: ability of a capacitor to store electrical energy
- higher capacitance = store more charge
- measured in Farads (F)

works by 2 metal plates separated by insulating material (called dielectric). when you apply voltage, one plate gets positive charge, the other gets negative charge

depends on:
- area of the plates: larger area increases capacitance
- distance b/w plates: smaller distance increases capacitance
- medium b/w plates (dielectric constant): higher dielectric constant (better insulating material) increases capacitance

metal type does not affect capacitance directly, mainly effects electrical conductivity, which is not a factor in the capacitance formula

43
Q

maximum transfer of power is when (R and r)

A

R = r

R: resistance of the load
r: resistance of the source (internal system)

  • if the resistances match up perfectly, get more flow going

think: in many systems, balancing 2 quantities often gives best performance

44
Q

1 Kilowatt-hour (per hour) is equal to how many joules?

A

3.6 x 10^6 or 3.6 MJ (megajoules)

45
Q

what factors does the speed of sound depend on?

A

temp: higher temps means molecules move faster which means transmit sound waves more quickly

density of medium: density affects how easily sound waves can travel through a substance

moisture (humidity): moist air (has water vapor) so less dense than dry air (which contains N and O particles), allowing sound waves to travel faster in moist air

pressure does not have any effect b/c density & pressure change in a way that they cancel each other out

46
Q

1 Gy (Gray)

A

equal to 100 rads or 1 J/kg or J kg^-1

  • SI init of absorbed radiation dose, represents amount of radiation absorbed per unit mass of a substance
47
Q

whats true about action and reaction? (Newton’s third law of motion - for every action, there is an equal & opposite reaction)

A

same nature: action and reaction forces are of the same type (e.g., both are gravitational, both are electrical, etc.)n
bp

same line: they act along the same line but in opposite directions

different bodies: they always act on different bodies, not on the same body. (ex. if you push on the wall, wall pushes back on you but they are acting on different bodies)

action and reaction cannot cancel each other out b/c they don’t act on the same body, can only cancel when act on the same body

48
Q

relative velocity concept

A

When two objects move in opposite directions, their relative velocity is the sum of their individual velocities.

  • ex. 2 buses moving across each other in opposite direction - their velocities relative to each other is both their individual velocities added together
49
Q

how to find the period of oscillation for a mass suspended from a spring

A

formula: 2π √M/k

M = mass, k = constant

but really just take the square root of the mass and multiple by the given time period so:

period of oscillation given = 1 sec
mass of spring = 16M

√16 = 4 x 1 = 4 sec

50
Q

volt x ampere is the unit of

A

equals watt, which is the unit of power

51
Q

dimensions of magnetic field strength & dimensions of magnetic induction

A

both have the same dimensions which are Newtons per ampere-meter or N/A*m

52
Q

which increase in pressure, the speed of sound will

A

remain the same

  • in general, increase/decrease in pressure has no effect on sound
53
Q

when a charged particle enters a magnetic field parallel to the field lines, it will

A

move straight

if it enters perpendicular to the magnetic field liens, it will deflect toward the north/south

54
Q

impulse

A

product of force and time
- also equal to the change in momentum

55
Q

different things to multiply force by

A

force x displacement = work done (J or Nm)
force x velocity = power (W or J/s)
force x acceleration - F = ma
force x time = impulse (change in momentum - Ns)

56
Q

how to solve this question:

how much work is done by force of gravity in pulling a stone of weight 10N from the top of a 250m high cliff to the foot of cliff?

A

Work = Force x Distance

so in this case, 10N x 250m = 2500 J

since all work is done by gravity going straight down, can neglect that part otherwise would have to do cos of that angle and multiply it by everything

57
Q

gravitational potential energy equation

A

U = -GMm/r

G = gravitational constant
M = mass of Earth
m = mass of object
r = distance from the center of the Earth

if Earth contracts to half size, radius divided by 2 and because inversely proportional, gravitational potential energy would double

58
Q

angular displacement formula

A

θ = s/r

θ = angular displacement
s = arc length (distance covered along circumference)
r = radius of the circle

59
Q

speed of wave formula

A

speed of the wave (v) = frequency (f) x wavelength (λ)

wavelength has to be in meters and waves in Hz or waves/second

60
Q

how to solve this question:

in a ripple tank 100 waves pass through a certain point in one second. If the wavelength of the wave is 1 cm then the speed of the wave will be?

A

speed of the wave (v) = frequency (f) x wavelength (λ)

1 cm -> 0.1 m
waves -> 100/sec

so 0.1 m x 100 sec = 1 ms^-1

61
Q

the domestic electricity supply in Pakistan has a frequency of

A

50 Hz

62
Q

in projectile motion, at maximum height, what is are the values of horizontal and vertical velocity?

A

horizontal velocity = constant
vertical velocity = 0

63
Q

magnetic flux is maximum when angle between magnetic field and vector area is

A

0º

64
Q

transformer

A

device that increases or decrease voltage (emf) in an alternating current (AC) circuit

works on the principle of electromagnetic induction

65
Q

transistor

A

small electronic component that acts like a switch or amplifier in circuits

  • it can turn a current on or off in a circuit, just like a light switch or can take a small electrical signal and make it bigger
  • are found in almost every electronic device, from computers to smartphones, because they help control and amplify the flow of electricity
66
Q

faraday’s law of electromagnetic induction

A

states that induced EMF (voltage) in a circuit is proportional to the rate of change of the magnetic flux through the circuit

so:

  • The faster you move the magnet or the stronger the magnet is, the more electricity you generate.
  • If you change the strength of the magnetic field or move the magnet faster, you make more electricity.

electromagnetic induction: process by which a chaining magnetic field induces an electric current in a conductor
- if you move a magnet near a wire, you can create electricity in the wire

67
Q

magnetic flux + 3 things it depends on

A

magnetic flux: how many magnetic field lines pass through a certain area. more lines pass through = stronger the magnetic flux

depends on:
strength of magnet: stronger magnets have more lines

area: bigger areas can catch more lines

angle: angle b/w magnet and wire affects how many lines go through

68
Q

time period and frequency

A

time period: time period it takes for one complete wave to pass a given point (secs)
- if you know frequency, you can find the time period using:

T = 1/f

frequency: number of waves that pass a point in one second (Hz)

69
Q

doppler effect

A

changing in frequency or wavelength of a wave in relation to an observer moving relative to the wave source

approaching source: if source of wave is moving towards observer, waves are compressed, causing frequency to increase (higher pitch or tone)

receding source: if source is moving away from observer, waves are stretched out, causing frequency to decrease (lower pitch or tone)

70
Q

simple harmonic motion (SHM) (+restoring force, angular frequency equation, energy)

A

type of repetitive, back and forth motion that follows a specific pattern
- ex. swinging pendelum or a mass on a spring

restoring force: always acts in the opposite direction to the displacement and is proportional to the displacement

angular frequency (ω)**
ω = 2π f

energy: total energy in SHM is constant, with kinetic and potential energy transforming into each other.

71
Q

how to solve this question:

a 10 N force moves a body around a circular path of radius 50 cm. What is the work done in completing one revolution?

A

zero

because no work is done on objects moving in circular motion

W = F x d x cos(angle)

72
Q

one complete circle is how many radian

A

2π radian

or 6.28

73
Q

stationary waves (aka standing waves) + kinetic/potential energy at nodes and antinodes

A

stationary waves: waves that seem to be standing wall, formed by interference of 2 waves traveling in opposite directions with the same frequency and amplitude

nodes: points on the wave where there is no motion (zero displacement). at nodes, all energy is potential (max displacement) (the area where the two waves intersect)

antinodes: when the waves are away from each other (the tops of them). at antinodes, wave alternates kinetic and potential energy
- when passes through equilibrium position = kinetic only

74
Q

when a vehicle moving in a straight path suddenly turns, the maximum force will be applied to which wheels

A

outer wheels

75
Q

acceleration due to gravity on the surface of the moon

A

g/6

76
Q

relationship b/w frequency and wavelength + spectrum of visible light

A

violet - blue - green - yellow - red

moving towards right in this order, wavelength increases so red has highest wavelength

but frequency decreases b/c inversely proportional

77
Q

which gas is used to fill an evacuated glass tube for gaining atomic spectra

A

hydrogen

78
Q
A

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