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MCAT - Physics > Class 7 > Flashcards

Class 7 Flashcards

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1
Q

What is Hooke’s Law?

A

F = -kx

F = restoring force
k = spring constant (spring-dependent)
`x = displacement from zero (relaxed position)
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2
Q

In a spring, what is amplitude?

A

The maximum value that x will have

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3
Q

How do you calculate the energy stored in a spring as it stretches/compresses?

A

PEelastic = 1/2kx^2

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4
Q

When a compressed spring extends, what is the work done by the spring?

A

Wby spring = - (delta)PEelastic

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5
Q

Does conservation of mechanical energy apply for a spring?

A

Yes

KEi + PEi = KEf + PEf

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6
Q

When is the maximum KE and PE of a spring?

A

Maximum KE is passing through equilibrium, moving quickly.

Maximum PE occurs when fully stretched or fully compressed.

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7
Q

What is the period in SHM?

A

The time it takes to complete one cycle

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8
Q

How do you calculate frequency?

A

f = 1/T

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9
Q

How do you calculate frequency for springs?

A

f = 1/2pi sqr.rt (k/m)

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10
Q

How do you calculate frequency for a pendulum?

A

f = 1/2pi sqr.rt (g/L)

L = length of pendulum arm
g = gravity
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11
Q

What is the restoring force for a pendulum?

A

Frestore = mgsin(theta)

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12
Q

What is a transverse wave?

A

A medium that oscillates perpendicular to the direction of wave propagation.

e.g. string, EM waves

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13
Q

What is a longitudinal wave?

A

A medium that oscillates parallel to direction of wave propagation.

e.g. sound (longitudinal pressure wave)

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14
Q

What is the opposite of wave compression?

A

Wave rarefaction (spreading out)

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15
Q

With regard to wave speed:

v =?

A

v = lambda x f

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16
Q

What determines the speed of a wave?

A

The medium and type of wave and physical properties of a medium

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17
Q

What is constant for all waves in a certain medium?

A

v

frequency or wavelength can change, however

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18
Q

What stays the same for waves when moving from one medium to another?

A

frequency

19
Q

What determines the speed of a wave in a string?

A

v = sqr rt. (tension/linear density)

20
Q

Do sound wave travel slower (than air) in water?

A

No, faster!

Sound waves are slowest in gases, faster in liquids, and fastest in solids

21
Q

What is the trend for sound wave speed in different phases?

A

Sound waves are slowest in gases, faster in liquids, and fastest in solids

22
Q

What is the beat frequency?

A

Cycles between constructive and destructive interference.

fb = | f1 - f2 |

23
Q

What is a standing wave?

A

A wave that is “waving” but not propagating because it is interacting with its own reflection (caused by a closed end of a tube) or tied down at both ends.

24
Q

What is a first harmonic wave?

A

n=1

A string tied at each end. 2 nodes and 1 antinode.

Length of strand is 1/2 of a wave so L = 1/2lambda

25
Q

What is a second harmonic wave?

A

n=2

3 nodes, 2 antinodes

L = lambda

26
Q

What is the generic equation for wavelength (lambda) of a string:

A

lambda(sub n) = 2L/n

27
Q

What is a third harmonic wave?

A

n=3

4 nodes, 3 antinodes

L = 3lambda/2

28
Q

In terms of waves, intensity I = ?

A

I = Power/Area

Power is the total energy
But intensity is per unit area so kids and adults can wear the same strength sunscreen.

29
Q

With regards to a spherical wave, how does intensity relate to distance from source?

A

I : 1/r^2

30
Q

How does intensity relate to amplitude?

A

I : A^2

Essentially the energy of a wave and the amplitude of a wave are directly related (shocker!)

31
Q

How do you human ears respond to sound intensity (mathematically)?

A

Logarithmically, which enables a larger sensitivity range

32
Q

What is the threshold for hearing?

A

Io = 10^-12 W/m

33
Q

What is the dB equation for hearing equation? What is the trick?

A

beta = 10log(sub10) I/Io

For every increase in the I by a factor of 10, ADD 10 to beta

For every decrease in I by a factor of 10, SUBTRACT 10 from b

34
Q

What is the doppler shift when the detector and the source get closer?

A

Higher detected frequency

35
Q

What is the doppler shift when the detector and the source get farther away?

A

Lower detected frequency

36
Q

What is the speed of sound in air?

A

350 m/s

37
Q

What is the equation for doppler shift?

A

x

38
Q

What is alpha emission?

A

Loss of 2 protons and 2 neutrons ->

Atomic number decreases by 2, mass number decreases by 4

39
Q

Is exposure to alpha decay?

A

Safe unless consumed

40
Q

What is beta emission?

A

Electron emission:
Loss of 1 electron from a neutron that gets split into an electron and a proton ->

atomic number increases by 1, mass number does not change

ORRRR

Positron emission:
A proton splits into a positron which is emitted and a neutron ->

Atomic number decreases by 1, mass number does not change

41
Q

What is electron capture?

A

A proton is combined with a (captured) electron to make a neutron.

Atomic number decreases by 1, atomic number does not change.

Same result as positron emission!

42
Q

What is gamma emission?

A

Atomic number and mass do not change.

Nuclei relaxes from an excited state.

43
Q

Nuclear reactions are ______thermic?

A

Exothermic

Decay, fission fusion, etc.

44
Q

Nuclear fission, fusion, etc.

(delta)E = ?

A

BEparent - BEdaughter

BE = binding energy

MCAT - Physics (9 decks)

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