Physics 106 Exam 4

Front 1

What is Einstein's first postulate?

Back 1

The laws are all the same in all inertial(non-accelerating)reference frames

Front 2

two cars hit and both say they were at rest. What do they agree on?

Back 2

Relative Velocity

Front 3

I am stationary in a reference frame but, if my frame system is not an inertial reference frame, then relative to me, a system that is an inertial reference frame must:

Back 3

Be accelerating

Front 4

Einstein’s theory of relativity is based in part on which one of the following postulates?
1.Space and time are absolutes
2.The speed of light in a vacuum is the same in all inertial reference frames
3.Energy is conserved only in elastic collisions

Back 4

The speed of light in a vacuum is the same in all inertial reference frames

Front 5

What is Einstein's second postulate?

Back 5

The speed of light in a vacuum is constant in all inertial reference frames--it does not depend on the velocity of the reference frame

Front 6

If the back rocket sent out a light pulse to warn the front rocket before the crash, who measures the speed of the light to be the fastest?

Back 6

they both measure it the same

Front 7

The relativistic effect of time dilation has been verified by which if the following?
1.The discovery of black holes
2.Muon experiments
3.Twin experiments
4.Red shift in distant galaxies
5.None of the above choices verified time dilation

Back 7

Muon Experiments

Front 8

A muon formed high in the Earth's atmosphere travels at a speed 0.990 c for a distance of 4.60 km (as we see it) before it decays. What is the muon's lifetime as measured in our reference frame?

Back 8

1.55e-5 seconds

Front 9

A knight on horseback holds a 10-m lance. The horse can run at 0.70 c. (It wins most of its races!) How long will the lance appear to a person that is standing still on the ground as the horse runs past?

Back 9

shorter than 10 m

Front 10

The observed relativistic length of a super rocket moving by the observer at 0.70 c will be what factor times that of the measured rocket length if it were at rest?

Back 10

.71

Front 11

According to the special theory of relativity, if a crew watches a movie that is two hours long in a spacecraft that is moving at high speed through space. Will an Earthbound observer, who is watching the movie through a powerful telescope, measure the duration of the movie?

Back 11

More than 2 hours

Front 12

According to the special theory of relativity, if a 30-year old astronaut is sent on a space mission is accelerated to speeds close to that of light, and then returns to earth after 20 years as measured on earth, what would be his biological age upon returning?

Back 12

Less than 50 years old

Front 13

We see a spaceship flying past at 0.9c. The captain of the spaceship launches a missile, which she sees leaving her ship at 0.9c out the front. We see the missile traveling at

Back 13

A speed less than c
or .99c

Front 14

A baseball at rest has
1. energy
2. mass
3. both

Back 14

both

Front 15

The number of photoelectrons emitted from a metal surface in the photo-electric effect experiments depends on

Back 15

The frequency of the incident light and the work function of the metal

Front 16

A beam of visible light is incident on the metal ball of an electroscope (hf < Φ) that is initially negatively charged. The electroscope . .

Back 16

nothing happens

Front 17

A beam of ultra violet light is incident on the metal ball of an electroscope (hf > Φ) that is initially negatively charged. The electroscope . .

Back 17

losses its negative charge

Front 18

400-nm wavelength light strikes a metal surface, a stream of electrons emerges from the metal. If the intensity of the light striking the surface is doubled

Back 18

more electrons ar emitted, but they do not have a higher energy

Front 19

When 400-nm wavelength light strikes a metal surface, a stream of electrons emerges from the metal. If the 400-nm light is replaced with 300 nm and the lamp is adjusted so that the intensity of the light striking the surface is the same as it was for the 400-nm light. With the 300-nm light,

Back 19

the electrons emitted are at a higher energy...shorter wavelength

Front 20

A beam of ultra-violet light is incident on the metal ball of an electroscope that is initially uncharged. Does the electroscope acquire a charge?

Back 20

Yes, it aquires a positive charge

Front 21

In the Compton experiment, the wavelength of the scattered light is ______________ the wavelength of the incident light.

Back 21

Longer than

Front 22

Suppose the momentum of a photon is determined with complete accuracy (the uncertainty approaches zero). The uncertainty in a simultaneous measurement of the photon’s position

Back 22

Approaches infinity,
cannot know the location and the momentum simultaneously

Front 23

What did the Rutherford alpha particle/gold foil experiment gave evidence for?

Back 23

Nuclear atom

Front 24

The green emission line in hydrogen is a transition from an excited state n=4 to n=2. The red line must be a transition from ______ to n=2.

Back 24

N=3 red is lower in energy than blue, so a smaller jump in n is needed to produce the light

Front 25

What is DeBoglie’s hypothesis?

Back 25

E=hf=hc/λ—Energy of a photon
p=E/c=h/λ—momentum of a photon
λ= h/p=h/mv—wavelength of a particle
If I increase the velocity of a particle, it decrease the wavelength
If an electron and a proton have the same wavelength, their momentum is the same but the electron has a much higher velocity.

Front 26

What is the mass of 12C?

Back 26

12u

Front 27

Notation review for elements
what is Z
What is N
What is A

Back 27

Atomic number-Z, # of protons in the nucleus
Determines which element it is
Neutron number-N, # of neutrons in nucleus
Mass number- A=Z+N

AZX

Isotopes—Nuclei of the same element (same Z) with different A (and N) values.

Front 28

Which of the following is an isotope of carbon?
a.13C6
b.13N7
c.13C7
d. they are all isotopes of carbon

Back 28

A. same number of protons, has one more neutron

Front 29

Which of the following is not a correct notation?
a. 13C6
b. 13N7
c. 13C7
d. they are all correct

Back 29

C.
13C7 says that there are 7 protons which lets us know that it is actually Nitrogen not carbon

Front 30

How many Protons does 263Sg106 have?

Back 30

106

Front 31

How many Neutrons does 263Sg106 have?

Back 31

157

263-106=157

Front 32

What is The half-life of a radioactive material is?

Back 32

The time required for half of the original number of atoms to decay.

Front 33

You start with 1000 dice. Every time you get a six you take it out. How many rolls is a half-life?

Back 33

4 rolls
there is a 1 in 6 chance everytime that you will remove a die

Front 34

If I start with 10000 pennies and every time I toss all the coins I remove the tails, how many tosses does it take to get down to less than a dollar left?

Back 34

7 tosses

each coin has a 50% chance each toss

Front 35

Over the course of 3 hours, 15% of a radioactive material decays. What is its half-life?

Back 35

12.8 hours

Front 36

true or false
If a nucleus undergoes radioactive decay it must be older than the other nuclei in the sample?

Back 36

False

Front 37

The nuclear force is really __________.

Back 37

a short range attractive force between nuclear particles.

Front 38

Can one element change into another element as a result of radioactive decay?

Back 38

yes

Front 39

Is Alpha Decay--42He given off in large or small nuclei

Back 39

Occurs in large nuclei—the result is a more stable nucleus with more neutrons compared to protons
22688Ra =>22286Rn + 42He

Front 40

What is Beta Decay

Back 40

Changes a proton to a neutron or a neutron to a proton--

146C => 147N + -1e + νe

189F => 188O + 1e + νe

Front 41

The neutrino is necessary in some radioactive decay to do what?

Back 41

conserve momentum

Front 42

What is gamma decay

Back 42

photon decay--change from a higher energy state to a lower energy state

152Dy66 => 152Dy66 + photon

Front 43

What type of decay is this?
238U92 => 234Th90 + ? T1/2 = 4.5 Gy

Back 43

alpha

Front 44

What type of decay is this?
234Th90 => 234Pa91 + ? T1/2 = 24 days

Back 44

beta -

Front 45

226Ra88 eventually becomes 206Pb82. What is released in this process?

Back 45

both alpha and beta, but more alphas than betas

Front 46

The boat of a pharaoh was discovered and dated to be 4,500 years old. The wood has ______ 14C6 for every trillion 12C6.

Back 46

less than 1 but more than .5. it will have .5 at 5,730 yrs, but we are not there yet

Front 47

Penetration depth for different types of radioactive decay

Back 47

alpha– only a few cm through air
Beta—only through air—blocked by paper or sheet of metal
Gamma rays—short wavelength light—penetrate several cm lead or a meter of concrete. Easily penetrates the skin and interacts with human cells—these are the dangerous ones.

Front 48

If you expose strawberries to high levels of radiation--

Back 48

They last longer

Front 49

What is nuclear fusion?

Back 49

the reaction that generates the sun's energy

Front 50

what does sustained nuclear fission require?

Back 50

1. a critical mass
2. incident neutrons

Front 51

what two factors determine whether the nuetrons will hit another Uranium?

Back 51

How fast they are moving
How far they move before they are out (critical mass)