physical science final exam (test 2)

Evaporation of a liquid is a cooling process. This means that A) the higher energy liquid molecules escape, leaving the lower energy molecules behind. B) the lower energy liquid molecules collide with and stick to a cooler surface, and cool that surface. C) the higher energy molecules give their energy to the lower energy molecules, lowering the average energy and thus the temperature of the liquid. D) all of the liquid molecules have the same energy; it is a cooling process because you have to put the liquid in the refrigerator (or some kind of cooler) in order to start the evaporation process.

A

In order for a force to do work on an object, the force and the displacement of the object must be A) parallel B) Perpendicular C) vertical D) horizontal

A

How much energy (Q, in calories) is required to raise the temperature of 10g of water from very cold (Ti = 3°C) to room temperature (Tf = 22°C)?

190cal

A depth-sounding vessel surveys the ocean bottom by sending out an ultrasonic pulse. The vessel receives the echo after t = 3 sec. If the pulse has a speed v=1530m/s, how deep is the ocean floor?

2295m

Calculate the kinetic energy of a 125 lb (m = 57 kg) skier moving at 20mph (v = 9.0 m/s). Answer numerically.

2308.5J

If the wavelength of a 288Hz tuning fork is measured to be λ = 1.19m, what is the wave speed (remember that v = λ f)?

342.7 m/s

An object is in motion when a force is applied to it. The force does negative work on the object. What does this mean? Doing negative work on an object A) will slow it down. B) will speed it up. C) will cause no change to its motion. D) will change its direction of motion (i.e., from +x to -y).

A

Compare the speed of sound through air to sound traveling through steel. A) Sound travels faster through steel because steel is an elastic material. B) Sound travels at the same speed through both, because the speed of sound is a constant. C) Sound travels faster through the air because air is less dense than steel (fewer molecules get in the way). D) No comparison can be made because the speed of sound also depends on temperature. At high temperature, steel is faster; but at low temps, air is.

A

Surprise! The eyeglass case falls off the edge of the table, which is 70cm (0.70m) above the floor. How much work does the force of gravity do on the case? A) W = [(0.120kg)(9.8m/s2)]×(0.70m) = 0.0823J B) W = (0.120N)×(0.70m) = 0.0823J C) W = (0.50N)×(0.70m) = 0.35J D) W = 0. Gravity is perpendicular to the motion!

A

Under what conditions will sound travel the fastest? A) Warm, humid air. B) Warm, dry air. C) Cool, dry air. D) Cool, moist air. E) Trick question. The speed of sound through air does not depend on either temperature or humidity!

A

What is the speed of sound through the vacuum of space? A) Zero. Sound cannot travel through space. B) Low, but not zero. Sound travels through space at the same speed as it travels through air, v ≈ 340m/s. C) High: sound travels through space at the same speed as it travels through steel, about v ≈ 6000m/s. D) Very high: sound travels through space at the same speed as light travels, v = 3×108m/s.

A

True or false: A welding spark, while having a very high temperature, actually contains very little heat.

true

True or false: An object may have either positive or negative potential energy.

true

True or false: If you transform chemical energy (breakfast) into mechanical energy (walking across campus), you will also generate waste heat.

true

True or false: Steel is an example of a very elastic material

true

True or false: The molecules of a solid material appear stationary, but they are continuously in motion.

true

True or false: With gravity (and all inverse-square relationships), when you triple the distance between two objects, the amount of force decreases by a factor of nine.

true

A transverse wave propagates A) parallel to the direction of the oscillation. B) perpendicular to the direction of the oscillation. C) neither parallel nor perpendicular to the propagation. D) not at all. Transverse waves only oscillate (while longitudinal waves only propagate).

B

As the skier slaloms downhill, her speed increases. If the skier is speeding up, A) kinetic energy is being converted into gravitational potential energy. B) gravitational PE is being converted into KE. C) kinetic energy is increasing for some unknown reason. There is no exchange betweenKE and PE.

B

Convection is A) the transfer of heat between objects that are not actually touching. B) the transfer of heat via bulk motion of the medium. C) the transfer of heat by electron and atomic collisions. D) the only way to transfer heat from a colder object to a warmer ones

B

For a sound to be audible to an average human, it must have A) a frequency between 10-12Hz and 1Hz. B) a frequency between 20Hz and 20,000Hz. C) a frequency between 40kHz and 40MHz. D) any frequency at all. Whenever molecules vibrate, human ears hear them.

B

If both liquids and gases are fluids, what is the difference between them? A) Liquids are made of molecules, while gases are made up of atoms. B) A liquid has fixed volume, but variable shape. Gases have both variable volume and shape. C) A liquid has almost zero cohesive bonding between molecules, while gases have strong cohesive bonds. D) All of these answers are accurate!

B

In the context of physics, work is A) a vector quantity representing an object's state of motion. B) a scalar quantity representing the process by which an object's state of motion can be changed. C) a constant quantity representing the mass of an object. D) that thing you do every day to earn a paycheck.

B

Dolphins can hear sound waves at very high frequencies-as high as 40,000 Hz. A sound wave with this high frequency. A) infrasonic B) audible C) ultrasonic D) radiosonic

C

In the context of physics, energy is A) a constant: all objects contain equal energy. B) a process: an object can do/perform energy. C) a property: an object can have/possess energy. D) a mystery. Physicists have no idea how energy works.

C

In the context of physics, what do we mean by conservation of energy? A) Energy is continually created, but without careful conservation, it will be easily destroyed. B) Energy cannot be created, so unless it is carefully conserved, it will be destroyed, leaving nothing. C) Energy cannot be created or destroyed; it can only be transferred from one object to another, or transformed from one type of energy to another. D) Energy cannot be created or destroyed. It cannot be transferred from one object to another, and it definitely cannot change form (like from electrical to mechanical).

C

Of the three phases of matter (solid, liquid, gas), which one demonstrates the weakest cohesive bonding between molecules? A) Solids. B) Liquids. C) Gases. D) Trick question. Cohesive strength does not depend on the phase of the matter; it's the same for all phases.

C

Surprise! The cat is knocking things off the table again. He applies a horizontal force of 0.5N to an eyeglass case with a mass of 120g (0.120kg). How much work did the cat do to move the case 15cm (0.15m) across the table? A) w=0.018J B) w=0.060J C) W= 0.075J D) W=0.240J E) W=0.300J F) W=).800J

C

When you decrease the temperature of a substance, the individual molecules will A) move faster, get farther apart, and occupy more space. B) move faster, get closer together, and occupy a smaller volume. C) move slower, get closer together, and occupy less space. D) move slower, slowly drift apart, occupy a greater volume of space.

C

Which of the following is a characteristic of the force of gravity between two masses? A) The force is inversely proportional to mass: the larger the mass, the smaller the force. Double the mass means half the force. B) The force is directly proportional to distance: the larger the separation between masses, the larger the force between them. C) The force is exclusively attractive. All mass is attracted to all other mass. D) The force may either attract or repel. Positive mass attracts positive mass, but repels negative mass.

C

A wave is A) an oscillation in time only. B) an oscillation in space only. C) an oscillation in space propagated through time. D) an oscillation in time propagated through space.

D

Consider a cube of metal (like we used in lab) with dimensions length L, width W, and height H. When you put it in boiling water and its temperature increases, it expands A) in zero dimensions, or not at all. The cube remains exactly the same size: L, W, and H remain unchanged. B) in one dimension only: L gets bigger, while W and H remain constant. C) in two dimensions: L and W increase, while H remains constant. D) in all three dimensions: L, W, and H all increase at the same rate.

D

Distinguish between an atom and a molecule. A) An atom is a single particle (like hydrogen). When two or more atoms are joined, it becomes a molecule (like water = H2O = 2 hydrogen atoms + 1 oxygen atom). B) An atom is the smallest particle of a solid, while a molecule is the smallest particle of a liquid or gas. C) An atom is a group of ten particles bonded together. Molecules are larger, and consist of 1 million particles bonded into a single unit. D) Technically, answer A is correct. However, for the purposes of Kinetic Theory, we can refer to either atoms or molecules as "molecules."

D

Temperature is defined as A) the average heat of an object. B) the average chemical potential energy per molecule of a substance. C) the average gravitational potential energy per molecule of a substance. D) the average internal kinetic energy per molecule of a substance. E) the energy transferred from one substance to another because of a temperature difference.

D

The specific heat of water is c = 1 cal/g·°C, and the the latent heat of vaporization is Lv = 540 cal/g. You have 10g of warm water initially at 45°C. How much total energy (Q) must be added to completely vaporize the entire 10g of water? A) Q = 1 cal/g·°C + 540 cal/g + 10 g + 45°C = 596cal B) Q = 540 cal/g + (100-45)°C = 595cal C) Q = (10g)(1cal/g·°C)(45°C)+(10g)(540cal/g) = 5850cal D) Q = (10g)(1cal/g·°C)(100-45)°C+(10g)(540cal/g)=5950cal

D

To say that potential energy is relative means that A) it was discovered by Einstein in 1905 when he was working on his calculations of special relativity. B) it cannot be measured. Any calculation of PE is just a guess, and may (or may not) be accurate in any way. C) it must always be calculated with respect to the ground (or the surface of whatever planet you happen to be standing on). It is meaningless and inaccurate to use any other reference for the calculation. D) you must always define a reference level, or a point (surface) at which h = 0, and the PE = 0. Depending on the situation you are analyzing, you might select a reference that is not the ground, but has meaning in the context of the problem.

D

Which of the following is not an example of molecular motion by diffusion? A) A drop of food coloring gradually turns an entire glass of water red. B) You can smell dinner cooking in the kitchen even if you are down the hall and in your bedroom. C) Boiling water poured over herb leaves in a mug results in a delicious cup of tea. D) You light a candle and the wax melts into a liquid pool surrounding the wick.

D

Heat is defined as A) the average temperature of an object. B) the average chemical potential energy per molecule of a substance. C) the average gravitational potential energy per molecule of a substance. D) the average internal kinetic energy per molecule of a substance. E) the energy transferred from one substance to another because of a temperature difference.

E

Specific heat is defined as A) the energy required to change the phase of a substance from solid to liquid. B) the energy required to change the phase of a substance from a liquid to a vapor. C) the energy transferred from one substance to another because of a temperature difference. D) the energy required to completely convert mass to energy, using Einstein's famous equation E = mc2. E) the energy required to raise the temperature of one gram of a substance by one degree Celsius.

E

Which of the following is not a form of potential energy? A) Gravitational. B) Electrical. C) Magnetic. D) Spring (or elastic). E) All of these are examples of forms of potential energy!

E

True or false: A swimming pool filled with water at 20°C contains far less heat than a welding spark at 5000°C.

false

True or false: An object may have either positive or negative kinetic energy.

false

True or false: As a wave propagates, the medium is carried along, also propagating in the same direction.

false

True or false: Some energy transformations are possible (like potential to kinetic), but other transformations are not possible (like mechanical to electrical).

false