Physics in the Summer Exam III
If a block of material has a mass of 16 grams and a volume of 8 cubic centimeters, what is its density?
2 grams per cubic centimeter D=M/V D=16/8 D=2
A ball lying on the floor does NOT coordinate the kinetic energy of its randomly moving atoms and suddenly leap up off the floor because
Although it could happen in principle, it is extremely unlikely.
12: ESSAY: States of Matter: know and describe them PLASMA
- not a common state of matter on Earth - the most common state of matter in the universe. - highly charged particles - has extremely high kinetic energy. The noble gases (helium, neon, argon, krypton, xenon and radon) are often used to make glowing signs by using electricity to ionize them to the plasma state. -Stars are essentially superheated balls of plasma.
12: ESSAY: States of Matter: know and describe them SOLIDS:
- particles are packed tightly together; - have low kinetic energy - atoms have a small vibration, but they are fixed in their position. - have a definite shape. - have definite volume. - cannot compress
12: ESSAY: States of Matter: know and describe them GASES
- particles have a great deal of space between them - have high kinetic energy. - If unconfined, the particles will spread out indefinitely; - if confined, it expand to fill its container. - has no definite volume - has no definite shape. When put under pressure by reducing the volume of the container, the space between particles is reduced, and the pressure exerted by their collisions increases. If the volume of the container is held constant, but the temperature of it increases, then the pressure will also increase.
14: Entropy
- refers to the idea that everything in the universe eventually moves from order to disorder, and entropy is the measurement of that change.
An object floats whenever its
-mass is less than the mass of an equal volume of the fluid. -weight is less than the weight of an equal volume of the fluid. -density is less than the density of the fluid.
12: ESSAY: States of Matter: know and describe them LIQUID/FLUID
-particles are not held in a regular arrangement, but are still very close - have more kinetic energy than those in a solid. - have a definite volume - cannot be compressed - have an indefinite shape - will change shape to conform to its container - Force is spread evenly; when an object is placed in it, it's particles are displaced by the object.
13: Work to thermal energy: joules to calories
1 cal = 4.2 J 1 J = .239 cal
11/1: If 1 g of hydrogen combines completely with 8 g of oxygen to form water, how many grams of hydrogen does it take to combine completely with 48 g of oxygen?
1 to 8: 48/8=6
13/16: What is the third law of thermodynamics?
Absolute zero can be approached experimentally, but can never be reached.
During a process, 28 J of heat are transferred into a system, while the system itself does 42 J of work. What is the change in the internal energy of the system?
ΔU = Q - W Q heat added W heat exhausted (work) 28-42= - 14J
****How many different arrangements can you make with three different colored blocks?
****idk
13: ****Work to thermal energy: if work doesn't not change KE or GPE of a system, where does the energy go?
***IDK "heat or friction" was the best I could do
Why don't the forces exerted inward on our bodies by the atmosphere crush our bodies?
The pressure inside our bodies is essentially the same as outside.
11/13. What is Boyle's law?
The product of gas volume and gas pressure is a constant. (PV = PV)
13: ESSAY: 3 types of heat transfer: Describe and give relevant state of matter: RADIATION
The transfer of energy through space/a vacuum. For example, in cooking, sun tea; or tea that is made by leaving the container outside in the sun and allowing the warmth to brew it.
Which has the larger density, a gold brick or a gold coin?
They have the same density
An engine takes in 7000 cal of heat and exhausts 2000 cal of heat each minute it is running. How much work does the engine do each minute?
W = ΔQin-ΔQexhausted 7000-2000= 5000 cal
14/2: How much work is performed by a heat engine that takes in 2050 J of heat and exhausts 1170 J?
W = ΔU - Q 2050-1170 = 880 J
What input energy is required if an engine performs 50 kJ of work and exhausts 60 kJ of heat?
W+E=total heat required 50+60 = 110kJ
Many scientists are worried about the adverse effects of global warming brought on by the greenhouse effect. What causes the greenhouse effect?
Water vapor and carbon dioxide block infrared radiation.
An artery can become partially blocked due to the formation of plaques. When a red blood cell passes through the narrowed section of such an artery, it experiences
a drop in pressure
In which of the systems listed below is the entropy decreasing?
a gas is cooled
12: Bernoulli's principle
an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. (The pressure in a fluid decreases as its velocity increases.)
12: Archimedes' principle
any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force the magnitude of which is equal to the weight of the fluid displaced by the body
The two fixed points used to define the modern Fahrenheit temperature scale are those of
boiling water and freezing water.
Which of the following is NOT a method of transporting thermal energy from one place to another? A. radiation B. condensation C. conduction D. convection
condensation
12/13: What is the basic force that binds materials together?
electrical attraction
In radiation, thermal energy is transported by
electromagnetic fields.
Tube A (smaller hole at top) and Tube B (hole at top is same as bottom) both contain water. The pressure at the base of A is
equal to the pressure at the base of B.
Is a sauna at a temperature of 202° F hotter or colder than one at 90° C? (F = (C temp * 9 / 5) + 32)
hotter 202-32= 170*5/9= 94.4° C > 90° C
13: ESSAY: 3 types of heat transfer: Describe and give relevant state of matter: CONDUCTION
is the process of heat being transferred between objects through direct contact. For example, in cooking, the electric burners on commercial stoves will conduct heat energy to the bottom of a pan sitting on top of it. From there, the pan conducts heat to its contents.
Under 11: Brownian motion
is the random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving molecules in the fluid.
The second law of thermodynamics says that
it is impossible to build a heat engine that can do mechanical work by extracting thermal energy that does not also exhaust heat to the surroundings.
Density is defined as
mass per unit volume
If 1 gram of hydrogen combines completely with 8 grams of oxygen to form water, how many grams of hydrogen does it take to combine completely with 32 grams of oxygen?
Ratio problem: 1/8= x/32 4
A typical jogger burns up food energy at the rate of about 40 kJ per minute. How long would it take to run off a piece of cake if it contains 400 Calories (about 1,700 kJ)?
Sadly: 42.5 min
11/10: An ideal gas has the following initial conditions: Vi = 475 cm3, Pi = 5 atm, and Ti = 100°C. What is its final temperature if the pressure is reduced to 1 atm and the volume expands to 1000 cm3?
T in kelvin: Ti = 100 + 273 = 373 K PiVi/Ti = PfVf/Tf 5 x 475/373 = 1 x 1000/Tf 6.367 = 1000/Tf Tf = 1000/6.367 = 156.06 K Convert back from Kelvin 157.06 -273.15 = -116.09 (please don't ask why kelvin was computed at 273 on top and 273.15 on the bottom...it's just how the damned computer wanted it)
Many people have tried to build perpetual-motion machines. Our study of physics tells us that perpetual-motion machines are
not possible to build.
Consider the human body to be a heat engine with an efficiency of 20%. This means that
only 20% of the energy you obtain from food can be used to do work.
12/19: Which is the most common state of matter in the universe?
plasma
Which of the four states of matter occurs at the highest temperature?
plasma
12/18: Which is the correct order of the states of matter of a substance, from COLDEST to HOTTEST?
solid, liquid, gas, plasma
An ice cube is floating in a glass of water. As the ice cube melts, the water level in the glass will
stay the same.
An aneurysm is a widening of an artery. This is dangerous because
the artery is likely to rupture
In conduction, thermal energy is transported by
the collisions of particles
13: What is latent heat?
the heat required to convert a solid into a liquid or vapor, or a liquid into a vapor, WITHOUT change of temperature.
13: specific heat
the heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree)
In convection, thermal energy is transported by
the movement of a fluid.
13/19: What happens while a material is changing state?
the temperature stays constant
13: Thermal Expansion: ΔL=LaΔT
the tendency of matter to change in shape, area, and volume in response to a change in temperature.
13: what is the first law of thermodynamics?
the total energy of an isolated system is constant; energy can be transformed from one form to another, but can be neither created nor destroyed.
12: What force binds atoms and molecules?
through a reaction known as chemical bonding.
Archimedes' principle tell us that the buoyant force is equal to the
weight of the displaced fluid
Which law of thermodynamics is the basis for the definition of temperature?
zeroth
13/10: What is the change in length of a metal rod with an original length of 5 m, a coefficient of thermal expansion of 0.00002/°C, and a temperature change of 18°C?
ΔL = L x a x Δtemperature 5 x .00002 x 18 = .0018m (or 1.8 mm - look at the units it wants)
What is the change in length of a metal rod with an original length of 4 m, a coefficient of thermal expansion of 0.00002/ ° C, and a temperature change of 30° C?
ΔL=aLΔT Length = 4m Coefficient a = 0.00002 ΔT = 30°C (0.00002)(4)(30)= .0024m = 2.4mm
14/22: What law of thermodynamics specifies a direction of time?
2nd Law: Arrow of time: the "one-way direction" or "asymmetry" of time. The thermodynamic arrow of time is provided by the Second Law of Thermodynamics, which says that in an isolated system, entropy tends to increase with time
***Given that the sulfur molecule has a mass of 32 amu, how many sulfur molecules are in 1 g of sulfur?
32 amu (1.66 x 10^-24)/1 amu = 5.312 x 10^-23 1g/5.312 x 10^-23 = 1.88 x 10^22
14/16: When a refrigerator does 150 joules of mechanical work and to extract 1250 joules of energy, how much energy is discharged as heat?
1250 + 150 = 1400 J
How much heat is required to raise the temperature of 500 g of water from 20° C to 50° C? Recall that the specific heat of water is 1 cal/g °C.
15,000 cal 30° x 500 g = 15,000
Which of the following is NOT a feature of our ideal gas? The gas particles A. are massless. B. have no internal structure. C. are indestructible. D. do not interact except when they collide.
A. are massless (ideal gases have a defined mass)
14/20: [The figure] shows the motions of atoms (a) in a falling ball and (b) after the ball hits the ground. Why would you not expect the ball on the ground to suddenly move upward?
Because it is exceedingly unlikely that the velocities of the atoms would simultaneously reorder themselves to generally point upward.
11/2: Given that 12 g of carbon combines completely with 16 g of oxygen to form carbon monoxide, how much carbon monoxide can be made from 36 g of carbon and 80 g of oxygen?
Carbon: 12 x 3= 36* (the limiting factor!) Oxygen: 16 x 3= 48 48+38= 84 grams
Rate hottest (1) to coldest (6) 100 degrees Celsius 4 degrees Celsius 0 Kelvin 1000 kelvin 32 degrees Fahrenheit 200 degrees Fahrenheit
Change all to Celsius: K --> C = -273° F --> C = -32° *5/9 1000K = 727° C 100°C = 100° C 200°F = 93° C 4°C = 4° C 32°F = 0° C 0 K = -273° C
Under 11: *****Random nuts to bolts question****
Definition of law of definite proportions. : a statement in chemistry: every definite compound always contains the same elements in the same proportions by weight.
12/11: A 470 cm³ block of aluminum (D = 2.7 g/cm³) is lowered carefully into a completely full beaker of water. What is the weight of the water, in newtons, that spills out of the beaker?
Density of water is 1g/m³ 470 cm³ x 1g/m³ = 470 g (0.470 kg) F = m x a 0.470 x 9.8 = 4.606 N
12/1: An object has a mass of 310 kg and a volume of 0.4 m3. What is its average density? Will it float in water?
Divide the mass by the volume. 310/0.4= 775 kg/m³ The density of water = 997 kg/m³ 997>775. If water has a greater density, it will float.
A heat engine takes in energy at a rate of 1600 W at 1000 K and exhausts heat at a rate of 1200 W at 400 K. What is the maximum theoretical efficiency of this engine? Recall efficiency can be calculated as: 1 - Tc/TH
E = 1-(Tc/Th) = 1-(400K/1000K) = 1-0.4= 0.60 0.60 x 100 = 60%
14/21: Which is a reasonable restatement of the second law of thermodynamics? A. Heat sometimes flows spontaneously from colder to warmer objects. B. The orderliness of the universe increases. C. Force equals mass times acceleration. D. Single-temperature heat engines can be built. E. All heat engines exhaust heat to their surroundings.
E. All heat engines exhaust heat to their surroundings.
A heat engine takes in 600 J of energy at 1000 K and exhausts 300 J at 400 K. What is the actual efficiency of this engine?
Efficiency η = work done / heat input = (heat input - heat rejected) / heat input = (600J - 300J) / 600J = 300 / 600 = 0.5 = 0.5 * 100% = 50%
14: Entropy: order vs. disorder
Example: an isolated region with hot and cold areas will, over time, converge to a more uniform, medium temperature. ie the temperature is initially non-random, but becomes more random.
13: ESSAY: 3 types of heat transfer: Describe and give relevant state of matter: CONVECTION
Heat transfer by the movement of currents within a fluid. For example, in cooking, a rotisserie chicken...air is blown around it with no direct contact with a heated surface.
13/15: What is the zeroth law of thermodynamics? ( I call it the no shit law)
If two objects are in thermal equilibrium with a third object, they are in thermal equilibrium with each other.
12/14: What can be said about the buoyant force on an object?
It is equal to the weight of fluid that the object displaces
Under 11: Which is NOT a characteristic of an ideal gas? -Its particles only interact with each other when they collide. -Its particles are indestructible. -Its particles have no internal structure. -Its properties and behavior are identical to those of air at atmospheric pressure. -It consists of an enormous number of tiny particles separated by large distances.
Its properties and behavior are identical to those of air at atmospheric pressure.
13/6: How many calories will it take to raise the temperature of a 38 g gold chain from 20°C to 120°C?
M x (specific heat) x Δ in temperature 38 x .031 x 100 = 117.8 J (.031 is the specific heat of gold)
14: ****What is a refrigerator?
Q = ΔU + W Q - Heat added to the system ΔU - change in the internal energy W - work done by system.. (on study paper)
14: ****What is a heat engine?
Q = ΔU - W Q - Heat added to the system ΔU - change in the internal energy W - work done by system.. (on study paper)
