AAMC 3 - Chem/Phys

Question 1

The relative thermodynamic stability of isomeric organic compounds can be inferred from which of the following types of experimental data?

A. Boiling points

B. UV–visible absorption spectra

C. Mass spectroscopic fragmentation patterns

D. Heats of combustion

Answer 1

D. Heats of combustion

AAMC Solution: The answer to this question is D because the relative thermodynamic stability of isomers can be determined based on the amount of heat produced when the compounds are combusted;

less heat, greater stability.

Question 2

Why does boiling point fail to measure thermodynamic stability of isomers?

Answer 2

The thermodynamic stability of a compound is determined by the INTRAmolecular forces.

Boiling points are a measure of the strength of INTERmolecular forces that hold molecules together.

Question 3

What determines thermodynamic stability?

Answer 3

The thermodynamic stability of a compound is determined by the INTRAmolecular forces.

Question 4

Will a more thermodynamically stable isomer produce more or less heat than a less stable isomer upon combustion?

Answer 4

A more thermodynamically stable isomer will produce LESS heat upon combustion.

Question 5

Heats of combustion measures the heat produced when compounds are combusted, or burned in oxygen. If less heat is produced, the compound is _____ stable; when more heat is produced, the compound is _____ stable to begin with. This is a great way to determine the thermodynamic stability of a compound.

Answer 5

Heats of combustion measures the heat produced when compounds are combusted, or burned in oxygen. If less heat is produced, the compound is more stable; when more heat is produced, the compound is less stable to begin with. This is a great way to determine the thermodynamic stability of a compound.

Question 6

Radioactive tritium (³H) labeled guanine has been used to measure the rate of biochemical processes that involve its binding or incorporation.

Given that water is the solvent for this type of experiment, what is the best site for tritium labeling?

A. I

B. II

C. III

D. IV

Answer 6

A. I

AAMC: The answer to this question is A, because the best site for tritium labeling would not exchange the tritium ions for protons in water. All of the N−H sites (II−IV) would readily exchange tritium protons due to their lone pair-facilitating protonation and subsequent tritium exchange with water, but the C−H site (I), lacking a lone pair, would retain its tritium label.

Question 7

Consider the following data.

Substance

• K*_a
• K* _w /K_a

H₂CO₃4.3 × 10^–72.3 × 10^–8HCO₃^–5.6 × 10^–111.8 × 10^–4

Based on these data, HCO₃^– is best categorized as:

A. a base since K_a > K_b for this ion.

B. a base since K_b > K_a for this ion.

C. an acid since K_a > K_b for this ion.

D. an acid since K_b > K_a for this ion.

Answer 7

B. a base since K_b > K_a for this ion.

AAMC: The answer to this question is B because K_b for HCO₃^– is larger than K_a for this ion. The value of K_b is given as K_w/K_a for H₂CO₃. By comparing K_a to K_b, it is clear that amphoteric HCO₃^– is more basic than acidic in water.

Question 8

In its lowest-energy electron configuration, zinc has a:

A. filled 3d energy level and a filled 4s energy level.

B. half-filled 3d energy level and a filled 4s energy level.

C. filled 3d energy level and a half-filled 4s energy level.

D. half-filled 3d energy level and a half-filled 4s energy level.

Answer 8

A. filled 3d energy level and a filled 4s energy level.

AAMC Solution: The answer to this question is A, based on subshell filling rules, the 12 valence electrons occupy 4s and 3d subshells, which are completely filled. Zn is element number 30 and in Group 12 of the Periodic Table.

Question 9

In some complexes, the central cation can be bonded to the same ligand in multiple places. This is called ________, and it generally requires large organic ligands that can double back to form a second (or even third) bond with the central cation.

________ therapy is often used to sequester toxic metals (lead, arsenic, mercury, and so on).

Answer 9

In some complexes, the central cation can be bonded to the same ligand in multiple places. This is called chelation, and it generally requires large organic ligands that can double back to form a second (or even third) bond with the central cation.

Chelation therapy is often used to sequester toxic metals (lead, arsenic, mercury, and so on).

Question 10

Define the period of a wave

Answer 10

The period is the amount of time from the beginning of a wave or signal to the beginning of the next wave or signal.

Question 11

What is the maximum energy of the UV photons generated by this plasma pencil? (Note: Speed of light is c = 3.0 × 10⁸ m/s; Planck’s constant is h = 6.63 × 10^–34 J•s; wavelength emitted is 200-300 nm)

A. 7 × 10^–16 J

B. 5 × 10^–17 J

C. 3 × 10^–17 J

D. 1 × 10^–18 J

Answer 11

D. 1 × 10^–18 J

AAMC Solution: The answer to this question is D because the energy of a photon is given by E = hf. The passage gives the wavelength of the UV radiation. Inserting this into the formula for photon energy yields:

E = hc/λ

= 6.6 × 10^-34 J × (3 × 10⁸ m/s)/(200 × 10^-9 m)

≅ 1 × 10^-18 J.

Question 12

That the electric field is uniform between the electrodes means that the electric field lines:

A. are more closely spaced at the positive electrode than at the negative one.

B. intersect halfway between the electrodes.

C. are more closely spaced at the negative electrode than at the positive one.

D. are equally spaced at both electrodes and between them.

Answer 12

D. are equally spaced at both electrodes and between them.

AAMC Solution: The answer to this question is D because, by definition, electric field lines are equally spaced in a uniform field.

Question 13

When two amino acids are joined via a peptide bond, what is the mass of the byproduct of this reaction? (Note: Assume that the amino acids were not modified by protecting groups.)

A. 17 amu

B. 18 amu

C. 32 amu

D. 44 amu

Answer 13

B. 18 amu

Peptide bonds are formed via a dehydration reaction.

The product of a dehydration reaction is water. What is the atomic mass of water?
Atomic mass H2O = 2(mass of H) + mass of O = 2(1)+16=18 amu

Question 14

What is an acetylation reaction?

Answer 14

The addition of a carbonyl bound to a methyl onto something else.

Question 15

What is the concentration of hydroxide ion for a solution with pH = 10?

A. 10^–10

B. 10^–6

C. 10^{– 4}

D. 10^–2

Answer 15

C. 10^{– 4}

Question 16

What is the resistivity of something with a maximum conductivity of 5.0 × 10^–3 (Ω∙cm)^–1?

A. 0.002 Ω•cm

B. 50 Ω•cm

C. 200 Ω•cm

D. 500 Ω•cm

Answer 16

Resistivity is the inverse of the conductivity

1/5.0 × 10^–3 (Ω∙cm)^–1 = 200 Ω∙cm.

Question 17

What aspect of a sigmoidal graph can help you measure its cooperativity?

Answer 17

The steepness of the curve

Question 18

Which halogen has the highest first ionization energy?

A. Iodine

B. Bromine

C. Chlorine

D. Fluorine

Answer 18

D. Fluorine

AAMC Solution: The answer to this question is D, because fluorine is the smallest halogen and appears at the top of the column of Group 17. With fewer electrons to shield the valence electron from the nucleus, fluorine will exhibit the highest first ionization energy.

Jack Westin Advanced Solution:

Fluorine is the halogen with the smallest radius and the fewest shielding electrons. It will have the highest first ionization energy and is the correct answer.

Question 19

Which of the following properties of a 2.3 MHz ultrasound wave remains unchanged as it passes into human tissues?

A. Frequency

B. Wave speed

C. Amplitude

D. Wavelength

Answer 19

A. Frequency

AAMC Solution: The answer to this question is A because the frequency of a wave is not affected by the medium through which it propagates.

Jack Westin Advanced Solution:

The frequency is determined by the source, not the medium through which the wave travels. It remains unchanged when a wave changes mediums and is the correct answer.

Question 20

Assume that in a study of rat tissues, fluid flows at a speed of 0.30 mm/s through a typical capillary opening of ~2.5 × 10⁴ μm² caused by a burst microbubble. Given this, which of the following is closest to the volume flow rate of fluid passing through the opening?

A. 4.5 × 10⁶ μm³/s

B. 7.5 × 10⁶ μm³/s

C. 1.2 × 10⁷ μm³/s

D. 4.5 × 10⁷ μm³/s

Answer 20

B. 7.5 × 10⁶ μm³/s

The answer to this question is B because the volume flow rate is given by velocity*area:

2.5 × 10⁴ µm² × 0.30 mm/s = 7.5 × 10⁶ µm³/s.

Question 21

Given that the speed of sound in the rat tissues was 1500 m/s with a frequency of 2.3 MHz, the wavelength of the ultrasound wave used in the study was closest to:

A. 34.5 mm.

B. 6.5 mm.

C. 1.5 mm.

D. 0.65 mm.

Answer 21

D. 0.65 mm

The answer to this question is D because the wavelength is given by v/f=wavelength

(1500 m/s)/(2.3 MHz) = 0.65 mm.

Question 22

What is the group name of these elements?

Answer 22

The post-transition metals

Question 23

What is the group name of these elements?

Answer 23

The Metalloids

Question 24

What is the group name of these elements?

Answer 24

The reactive non-metals

Question 25

If a reaction is spontaneous, the value of K must be:

A. greater than 1.

B. equal to ΔG.

C. less than 1.

D. equal to zero.

Answer 25

A. greater than 1.

The answer to this question is A, because a spontaneous reaction is one that exhibits ΔG < 0.

Since ΔG= –RTln(K_eq), this means that K_eqmust be > 1 in a spontaneous reaction.

Question 26

Which of the following molecules has an octahedral geometry?

A. SF₆

B. CBr₄

C. XeF₄

D. BrF₃

Answer 26

A. SF₆

The answer to this question is A because SF₆ is an AX₆system with no lone pairs. As a result, SF₆ will adopt an octahedral bonding arrangement to minimize the repulsive interactions of the bonding domain electrons.

Question 27

A tall tube is evacuated, and its stopcock closed. The open end of the tube is immersed into a container of water (density 10³ kg/m³) that is open to the atmosphere (pressure 10⁵ N/m²).

When the stopcock is opened, how far up the tube will the water rise?

A. 1 m

B. 5 m

C. 10 m

D.20 m

Answer 27

C. 10 m

The answer to this question is C because the water will rise to a height such that the weight (mass multiplied by gravitational acceleration) of the water column equals the atmospheric pressure multiplied by the tube cross-sectional area A.

Because mass is density times volume, it follows that 10³ kg/m³ × h × A × 10 m/s² = 10⁵ N/m² × A, where h is the height sought.

Solving for h yields h = 10⁵ N/m²/(10⁴ N/m³) = 10 m.

Question 28

Which of the following is a second period element that is a covalent network solid in its standard state?

A. Carbon

B. Phosphorous

C. Oxygen

D. Iodine

Answer 28

A. Carbon

The answer to this question is A because Carbon is a second period element and carbon is a covalent network solid (graphite) in its standard state.

Oxygen is a gas (O₂) in its standard state

Question 29

Nickel-metal hydride (NiMH) batteries are rechargeable cells used in many hybrid and all-electric vehicles. An NiMH battery in the process of recharging is similar to:

A. An electrolytic cell

B. A galvanic cell

C. A concentration cell

D. A half-cell

Answer 29

A. An electrolytic cell

In essence, rechargeable batteries work via reversible redox processes. When such a cell is discharging, it is releasing stored energy; this is similar to the spontaneous process seen in galvanic cells.

However, this question asks about recharging. Here, we must use an external power source to move electrons in a way that would be naturally nonspontaneous, just as an electrolytic cell does.

Question 30

A vacuum has an index of refraction of 1.0, while that of liquid water is around 1.33. With this in mind, how much more rapidly will infrared light travel than ultraviolet light when both are moving through outer space?

A. IR rays will travel 1.33 times faster than UV rays.

B. UV rays will travel 1.33 times faster than IR rays.

C. Both forms of ray will move at the same speed.

D. This answer cannot be determined without knowing the relative frequencies of the two rays.

Answer 30

C. Both forms of ray will move at the same speed.

Both IR and UV – along with visible light, microwaves, and a number of other forms – are types of electromagnetic radiation, commonly known as “light.” All types of light move equally quickly in a vacuum, like that present in space. Specifically, they travel at 3 × 10⁸ m/s.

Question 31

What product is produced when 2-hexanol successfully reacts with chromium(III) oxide?

A. Hexanoic acid

B. 2-hexanone

C. Hexane

D. 1,2-hexanediol

Answer 31

B. 2-hexanone

B is correct. Like many chromium-containing reagents, chromium(III) oxide, or Cr2O3, is a strong oxidizing agent. In general, such reagents increase the number of bonds formed between carbon and oxygen and decrease those between carbon and hydrogen. Here, we begin with 2-hexanol, a secondary alcohol. Oxidizing this molecule as thoroughly as possible results in production of the corresponding ketone, shown below.

Question 32

Which of the following compounds is a strong acid?

A. Nitrous acid

B. Hypochlorous acid

C. Perchloric acid

D. Sulfurous acid

Answer 32

C. Perchloric acid

Perchloric acid (HClO₄) is one of the strong acids you should know for the MCAT.

Question 33

Where does this chemical reaction take place?

A. In the mitochondria of skeletal muscle only

B. In the mitochondria of all cells

C. In the lacteals of the lymph system

D. In the lumen of the small intestine

Answer 33

D. In the lumen of the small intestine

This reaction involves the breakdown of triacylglycerides into glycerol and fatty acids. While it may take place in a number of places, of those listed, only D is correct. Lipase released by the pancreas into the small intestine catalyzes this reaction.

Question 34

This molecule is adenosine triphosphate, or ATP.

When adenylate cyclase reacts with ATP, cyclic AMP is formed. What is/are the other product(s) of this reaction?

A. 2 H₂O

B. Pyrophosphate

C. 2 P_i

D. ADP

Answer 34

B. Pyrophosphate

If it is known that ATP goes to AMP, two phosphate groups must be lost; thus a pyrophosphate (or double phosphate group) is the side product of this reaction.

Question 35

How can the role of calcitonin, especially its control over serum [Ca+2], best be described?

A. Calcitonin stimulates osteoblasts, therefore decreasing serum [Ca+2].

B. Calcitonin stimulates osteoblasts, therefore increasing serum [Ca+2].

C. Calcitonin stimulates osteoclasts, therefore decreasing serum [Ca+2].

D. Calcitonin stimulates osteoclasts, therefore increasing serum [Ca+2].

Answer 35

A. Calcitonin stimulates osteoblasts, therefore decreasing serum [Ca+2].

Calcitonin “tones down” blood calcium levels by activating osteoblasts. Osteoblasts synthesize hydroxyapatite, a calcium-containing mineral. In other words, these cells absorb excess calcium in the blood with the goals of both synthesizing new bone and lowering serum calcium levels.

Question 36

High levels of which molecule will inhibit the TCA cycle?

A. AMP

B. ADP

C. NADH

D. NAD⁺

Answer 36

C. NADH

Products of the TCA cycle will act to inhibit it. These include ATP, citrate, and NADH.

In contrast, high levels of low-energy molecules such as AMP, ADP, and NAD⁺ stimulate the TCA cycle. therefore stimulated in times of high acetyl-CoA. Pyruvate carboxylase is an enzyme used in gluconeogenesis that converts pyruvate to oxaloacetate, during high levels of acetyl-CoA gluconeogenesis is stimulated. Pyruvate dehydrogenase is responsible for conversion of pyruvate to acetyl-CoA and is therefore inhibited in times of high acetyl-CoA.

Question 37

During the Krebs cycle, fumarate and water unite to form malate. How can this type of chemical reaction best be described?

A. Dehydration

B. Hydration

C. Hydrolysis

D. Decarboxylation

Answer 37

B. Hydration

During the synthesis of malate, fumarate experiences the addition of water across its double bond. This results in the replacement of this bond with an –OH group on one carbon and a hydrogen atom on the other. Such a process represents a classic hydration reaction.

Question 38

Glycolysis is a process used to help regulate blood sugar. Eight hours after a meal, what is the expected level of glucose saturation for hexokinase and glucokinase?

A. Hexokinase will be saturated, while glucokinase will be unsaturated.

B. Hexokinase will be unsaturated, while glucokinase will be saturated.

C. Both enzymes will be saturated.

D. Both enzymes will be unsaturated.

Answer 38

A. Hexokinase will be saturated, while glucokinase will be unsaturated.

Hexokinase has a much higher affinity for glucose than its isozyme, glucokinase. Therefore this enzyme will be saturated with glucose at much lower concentrations. Eight hours after a meal is long enough to imply fairly low blood sugar, making glucokinase inactive due to its low affinity.

Question 39

The renin-angiotensin system regulates blood pressure by stimulating which two mechanisms?

A. Promotion of aquaporins and vasoconstriction

B. Sodium reabsorption and vasoconstriction

C. Potassium reabsorption and vasodilation

D. Glucose reabsorption and vasodilation

Answer 39

B. Sodium reabsorption and vasoconstriction

The renin-angiotensin system results in the secretion of aldosterone. This steroid hormone regulates blood pressure by increasing the reabsorption of sodium. Water naturally follow the movement of sodium, thus increasing blood pressure and decreasing urine output. Vasoconstriction is another main effect of aldosterone, as it also increases BP.

Question 40

In a healthy patient, which area of the renal interstitium has the highest solute concentrations?

A. Renal hilum

B. Outer medulla

C. Inner medulla

D. Cortex

Answer 40

C. Inner medulla

As you travel from the cortex towards the inside of the kidney, or the medulla, the solute concentration increases. Solute concentration reaches its highest in the loop of henle.

Question 41

Low calcium intake will directly result in the increased activity of which cells?

A. Osteoblasts

B. Osteoclasts

C. Fibroblasts

D. Macrophages

Answer 41

B. Osteoclasts

As blood calcium levels drop, the endocrine system via parathyroid hormone will increase the activity of osteoclasts to break down bone and provide calcium.

Question 42

Chymotrypsin is an intestinal enzyme that is used to digest proteins. In the absence of food, chymotrypsin does not digest any non-target proteins because chymotrypsin:

A. is activated allosterically by leucine, an essential amino acid that can only be found in the diet.

B. is synthesized as a zymogen, which is activated by other digestive enzymes in the presence of food.

C. is localized to the duodenum, which is coated in an enzyme-resistant mucus.

D. has an active site that can only bind to non-native proteins.

Answer 42

B. is synthesized as a zymogen, which is activated by other digestive enzymes in the presence of food.

You must recall that many digestive enzymes are synthesized as zymogens.

Question 43

If hexanamide is treated with ethanol, what would be the expected products?

A. Hexanamide

B. Hexanamide and water

C. Hexanoic acid and an amine

D. Hexanoic acid

Answer 43

A. Hexanamide

The amine group is a stronger nucleophile than ethanol, and thus has less propensity to leave the amide. Amides are significantly more stable than esters.

Question 44

Which choice is an accurate statement about electron affinity?

A. It reflects an endothermic process for both bromine and potassium.

B. It reflects an exothermic process for both bromine and potassium.

C. The process that it reflects is endothermic for bromine but exothermic for potassium.

D. The process that it reflects is exothermic for bromine but endothermic for potassium.

Answer 44

D. The process that it reflects is exothermic for bromine but endothermic for potassium.

To establish a complete octet, bromine needs only one additional electron. Therefore, when bromine adds an electron, it will become more stable and release energy. Potassium, in contrast, prefers to lose an electron to have a full octet. For this element, adding another electron is unfavorable and will require energy in an endothermic process.

Question 45

If equimolar amounts of the molecules below are added to two identical containers of pure water, which solution will display the lower boiling point?

A. the solution containing Molecule Z, due to its higher molecular weight

B. the solution containing Molecule X, due to its lower molecular weight

C. the solution containing Molecule Z, due to its higher Van’t Hoff factor

D. the solution containing Molecule X, because it dissociates into fewer total particles

Answer 45

D. the solution containing Molecule X, because it dissociates into fewer total particles

As a dicarboxylic acid, Molecule Z will dissociate in water; specifically, both of its carboxylic acid groups will be deprotonated. This results in more total particles than the solution containing Molecule X, a neutral amide. Since all other factors are identical, the solution with fewer particles will show a smaller degree of boiling point elevation.

Question 46

A spring system is shown below, with m representing the mass attached to the spring, k representing the spring constant, and x denoting the distance stretched or compressed from the spring’s equilibrium position.

What is the highest velocity this mass can achieve upon its release?

A. k/m

B. 0.5kx²

C. (x)(k/m)^1/2

D. x²k/m

Answer 46

C. (x)(k/m)^1/2

The maximum kinetic energy possessed by the spring, if assumed to be ideal, is equal to its maximum elastic potential energy. If we set the elastic PE of a spring system (U = ½ kx²) to the kinetic energy of the block, we get kx² = mv². Solving for v yields choice C.

Question 47

4-tert-butylcyclohexanol can be classified as:

A. a primary alcohol.

B. a secondary alcohol.

C. a tertiary alcohol.

D. a quaternary alcohol.

Answer 47

B. a secondary alcohol.

The structure of this molecule is shown below.

As indicated by this diagram, the hydroxyl group is located on a different ring carbon than the tert-butyl group. The –OH oxygen is thus bound to a carbon that is attached to only two alkyl substituents. This is the definition of a secondary alcohol.

Question 48

Solid carbon dioxide, commonly known as “dry ice,” has a variety of uses in the cooling and packaging industries. A reaction involving this compound is shown below.

CO₂ (g) → CO₂ (s)

This type of reaction is known as:

A. Sublimation

B. Condensation

C. Deposition

D. Decomposition

Answer 48

C. Deposition

The reaction shows carbon dioxide undergoing a phase change from gas directly to solid. Such a transition is termed deposition.

Question 49

Destructive interference occurs in photodiode detectors when direct and scattered light rays take paths to the photocell that differ in phase by:

A. 0 degrees.

B. 90 degrees.

C. 180 degrees.

D. 360 degrees.

Answer 49

C. 180 degrees.

Jack Westin: Destructive interference occurs when two waves are shifted by half a wavelength. Think of one wavelength as one revolution. So, 360 degrees would be one wavelength and 180 degrees would be half a wavelength.

Question 50

The lowest frequency (longest wavelength) of a standing wave that can be supported in a given length of string is known as the ___________.

Answer 50

The lowest frequency (longest wavelength) of a standing wave that can be supported in a given length of string is known as the fundamental frequency (first harmonic).

Question 51

What is the fundamental frequency?

Answer 51

The lowest frequency (longest wavelength) of a standing wave that can be supported in a given length of string is known as the fundamental frequency (first harmonic).

Question 52

What trend is seen between the wavelength and harmonic number?

Answer 52

As harmonic number increases, wavelength decreases.

The 1st harmonic (fundamental frequency) has the largest wavelength, the 2nd has a smaller wavelength, the 3rd has an even smaller wavelength, etc.

Question 53

What trend is seen between harmonic number and frequency?

Answer 53

As harmonic number increases, frequency increases.

The 1st harmonic (fundamental frequency) has the lowest frequency, 2nd harmonic has a higher frequency, 3rd has an even higher, etc.

Question 54

What trend is seen between harmonic number and period?

Answer 54

As harmonic number increases, period decreases.

This is clear because as harmonic number increases, frequency increases. Period is T = 1/f, so as frequency increases, period decreases.

Question 55

As a shortcut, for strings attached at both ends, the number of ________ present will tell you which harmonic it is.

Answer 55

As a shortcut, for strings attached at both ends, the number of antinodes present will tell you which harmonic it is.

Question 56

As a shortcut, for open pipes (pipes open at both ends), the number of ______ present will tell you which harmonic it is.

Answer 56

As a shortcut, for open pipes (pipes open at both ends), the number of nodes present will tell you which harmonic it is.

Question 57

If the source of a sound is moving away from you, what happens to the wavelength of the sound by the time it reaches you?

Answer 57

The wavelength increases

Using the doppler effect equation, we know that an emitted sound from a source moving away from us will result in a lower frequency (slower oscillations), this means that it must have a larger wavelength.

Question 58

If the source of a sound is moving towards you, what happens to the wavelength of the sound by the time it reaches you?

Answer 58

The wavelength decreases

Using the doppler effect equation, we know that an emitted sound from a source moving towards us will result in a higher frequency (faster oscillations), this means that it must have a shorter wavelength.

Question 59

An astronomer observes a hydrogen line in the spectrum of a star. The wavelength of hydrogen in the laboratory is 6.563 x 10^-7m, but the wavelength in the star’s light is measured at 6.56186 x 10^-7m. Which of the following explains this discrepancy?

A. The star is moving away from Earth.

B. The wavelength of light that the star is emitting changes constantly.

C. The frequency of light that the star is emitting changes constantly.

D. The star is approaching Earth.

Answer 59

D. The star is approaching Earth.

Jack Westin: To answer this question, we have to understand the relationship between wavelength, frequency, and the Doppler effect.
The wavelength of the hydrogen in the star’s light is slightly shorter than the wavelength in the laboratory. Frequency is inversely proportional to the wavelength. This means that the frequency of the arriving star light is higher than normal. Increased frequency means that the source is moving toward us. A deceased frequency would mean the opposite.

Think of it this way. The classic example is the ambulance siren. It has a higher pitch, or a higher frequency, when the ambulance moves toward us. That’s what we see here.

Question 60

An astronaut on Earth notes that in her soft drink an ice cube floats with 9/10 of its volume submerged. If she were instead in a lunar module parked on the Moon where the gravitation force is 1/6 that of Earth, the ice in the same soft drink would float:

A. with more than 9/10 submerged.

B. with 9/10 submerged.

C. with 6/10 submerged.

D. totally submerged.

Answer 60

B. with 9/10 submerged.

Jack Westin: This is a question that’s fairly easy to visualize. Think about a soft drink to which you add ice. Part of some cubes are submerged, while parts of them may float above the soft drink. What are the forces acting on the cube? We have gravitational force down, while the buoyant force is in the opposite direction. That buoyant force (FB = Vρg) is what is allowing the cube to float. We can set the forces equal to one another:

(mass of the ice cube) x (g) = (volume cube submerged) (density of soft drink) (g)

The key here is that we have “g” on both sides of our equation. If we have 1/6th of g on both sides, then both sides of the equation are affected equally. What does that mean for our question? Even with gravitation force being 1/6 that of earth, the cube would not change how much it floats.

Question 61

What equation is used to find the force on a charged particle in an electric field?

Answer 61

F = qE

F - force on the charged particle

q - charge of the particle

E - electric field strength

Question 62

If you need to find the acceleration of a charged particle with a given mass, q (charge), and E (electric field), how is this done?

Answer 62

F and acceleration are directly proportional. We can find force on the particle by F=qE.

Now we have force of the particle. We also know F=ma. We can use this to set the equations equal to each other:

qE=ma

Rearranging, we get qE/m=a

Question 63

Can capacitors and batteries BOTH be considered circuit elements that store energy?

Answer 63

Yes.

Capacitors and batteries both store energy.

U_cap=½CV²

Batteries use Volts, V=J/c, meaning energy per charge.

Question 64

A block of weight W is pulled across a rough floor by a rope that exerts a force T on the block. The frictional force between the floor and the block is F. Which of the following expressions equals the frictional force F when the block moves with a constant speed?

A.T

B.W – T

C.T sin θ

D.T cos θ

Answer 64

D.Tcos θ

AAMC: Because the object moves at a constant speed, the net force on the object is zero. In the horizontal direction the sum of the forces must be zero. This will occur if the horizontal component of T, T cos θ, has the same magnitude as the frictional forceF. Thus, D is the best answer.