Two balls, one mass 5 kg and the other mass 10 kg, are dropped simultaneously from a window. When they are 1 m above the ground, the balls have the same
A bomb dropped from an airplane explodes in midair
its total kinetic energy increases
The operation of a rocket is based upon
conservation of linear momentum
When a spinning skater pulls in her arms to turn faster
her angular momentum remains the same
The work done in holding a 50 kg object at a height of 2 m above the floor for 10 s is
The work done in lifting 30 kg of bricks to a height of 20 m is
A total of 4900 J is used to lift a 50 kg mass. The mass is raised to a height of
The work a 300 W electric grinder can do in 5.0 min is
A 150 kg yak has an average power output of 120 W. The yak can climb a mountain 1.2 km high in
A 40 kg boy runs up a flight of staris 4 m high in 4 s. His power output is
Car A has a mass of 1000 kg and is moving at 60 km/h. Car B has a mass of 2000 kg and is moving at 30 km/h. The kinetic energy of car A is
twice that of car B
A 1 kg object has a potenital energy of 1 J relative to the ground when it is at a height of
A 1 kg object has a KE of 1 J when its speed is
The 2 kg blade of an ax is moving at 60 m/s when it strikes a log. If the blade penetrates 2 cm into the log as its KE is turned into work, the average force it exerts is
A 1 kg ball is thrown in the air. When it is 10 m above the ground, its speed is 3 m/s. At this time m0st of the ball's total energy is in the form of
A 10,000 frieght car moving at 2 m/s collides with stationary 15,00 kg freight car. The two cars couple together and move off at
A 30 kg girl and a 25 kg boy are standing on frictionless roller skates. The girl pushes the boy, who moves off at 1.0 m/s. The girls speed is
(W) a process that transfers energy to an object when an object is moved against an opposing force or from rest.
the rate of doing work. P=W/t
energy due to motion
types of energy
-Chemical- fuels -Mechanical- potential and kinetic (push, pull, drop) -Electrical- energy of moving charges Ex: used to turn motors -Radiant- energy that travels through space Ex: from the sun -Nuclear- changes in the nucleus of an atom
law of conservation of energy
energy can be neither created or destroyed (energy is conserved)
law of conservation of momentum
in the absence of outside forces, the total momentum of a set of objects remains the same no matter how the objects interact with one another.
the measure of the tendency to keep moving at the same speed in the same direction.
the rush of the gases out of the rockets is balanced by the rocket moving upward and thus the total momentum of the entire system=zero!
the measure of the tendency to keep spinning at the same speed in the same direction
law of angular momentum
an object that is spinning tends to keep spinning
a spinning body tends to maintain the direction of its spin axis as well as the amount of angular momentum
a relative measure of the amount of heat in a substance. Also, the property that gives rise to sensations of hot and cold.
(unit=Joule) the sum of all kinetic energies of all the separate particles that make up an object (also called initial energy)
specific heat capacity
(unit= kj/kg*C) the amount of heat that must be added to or removed from an object to change its temperature by 1 degree C. Q=mc(change in temp).
the biochemical processes by which the energy content of food an animal eats is liberated
(Fb) the difference between the force pulling down on the object (gravity) and the force pushing up on the object (fluid pressure)
buoyant force on an object in a fluid = weight of fluid displaced by the object. - This principle holds if the object sinks or floats. - If the object's weight is greater than the buoyant force, it sinks vice versa
at a constant T and n, the V of any gas is inversely proportional to the applied (external) P on the gas.
at a constant P and n, the v of any gas is directly proportional to the T of the gas.
ideal gas law
is a mathematical expression relating Boyle's, Charles's and Gay-Lussac's laws at constant number of moles. P1V1/T1=p2V2/T2
kinetic theory of matter
the energy of molecular motion; it is the energy that tends to disorganize matter.
the temp at which liquid rapidly begins to turn to gas
the temp at which a solid turns to a liquid (also called fusion)
a device that turns heat into mechanical energy. Ex: gasoline engine or steam turbine at a power plant
the study of heat transformation
first law of thermodynamics
energy cannot be created nor destroyed only converted from one form to another.
second law of thermodynamics
it is impossible to take heat from a source and change all of it to mechanical energy or work; some heat must be wasted.
the measure of the disorder of molecules in a substance
the flow of charge from one place to another
if we connect a wire between the + and - terminals of a battery we get an electrical circuit. The flow of electrons can be measured as a rate which is called an ampere.
electrical potenial energy
charge * potential energy difference. Measured in Volts (V).
I=V/R, where I= current, V= voltage, R= resistance
joined end to end, current flows through all
joined through different connections, current split between each
how much mechanical work you can get out of this particular system. P=IV
a substance through which electric charge can flow readily. Ex: Metals
a substance through which electric charge has a difficult time (no to little conductivity). Ex: glass, rubber, plastic, sand, dirt, wood.
in between a conductor and an insulator in its ability to conduct electricity. Semiconductors are used to make transistors, which are devices that can be used as a tiny switch in electrons. Ex: Silicon, germanium
a substance that allows electricity to flow through it with zero resistance.
a magnet is an object that has a north and south pole and it attracted to other magnets.
the altered space around a mass (gravity force), and electric charge (electrostatic force), or a magnet force (magnetic force).
he noticed that a compass lines up perpendicular to a wire with current running through it. All moving electric charges give rise to magnetic fields!
right hand rule
if we point our thumb on our right hand in the direction of the current flow, our fingers point in the direction of the magnetic field.
a coil of electric wires with a core of iron.
a device that creates electricity from mechanical energy
only goes in one direction and comes from a constant source like a battery
Two thermometers, one calibrated in degrees F and the other in degrees C, are used to measure the same temperature. The numerical reading on the fahrenheit thermometer
may be any of these, depending on the temperature
One gram of steam at 100 degrees C causes a more serious burn than 1 g of water at 100 degress C because steam
contains more energy
heat transfer in a gas can occur by
radiation, convection, and conduction
heat transfer in a vacuum can occur by
The fluid at the bottom of a container is
under more pressure than the fluid at the top
The pressure of the earths atmosphere at sea level is due to
the gravitational attraction of the earth for the atmosphere
A cake of soap placed in a bathtub of water sinks. The buoyant force on the soap is
less than its weight
The density of freshwater is 1.00 g/cm3 and that of seawater is 1.03 g/cm3. A ship will float
lower in freshwater than in seawater
An icecube whose center consists of liquid water is floating in a glass of water. When the ice melts, the level of water in the glass
remains the same
A person stands on a very sensitive scale and inhales deeply. The reading on the scale
any of the above, depending on how the expanision of the persons chest compares with the volume of air inhaled
At constant pressure the volume of a gas sample is directly proportional to
its absolute temperature
which of the following statement is not correct
all molecules have the same size and mass
molecular motion is not responsible for
absolute zero may be regarded as that temperature at which
molecular motion in a gas would be minimum possible
on a molecular level heat is
at a given temperature
the molecules in a gas all have the same average energy
the temperature of a gas sample in a container of fixed voume is raised. The gas exerts a higher pressure on walls of its container because its molecules
have higher average velocities and strike the walls more often
The volume of a gas sample is increased while its temperature is held constant. The gas exerts a lower pressure on the walls of its container because its molecules strike the walls
When evaporation occurs, the liquid that remains is cooler because
the slowest molecules remain behind
When vapor condenses into a liquid
it gives off heat
Food cooks more rapidly in a pressure cooker than in an ordinary pot with a loose lid because
the high pressure raises the boiling poinht of water
A heat engine takes in heat at one temperature and turns
some of it into work and ejects the rest at a lower temperature
In any process the maximum amount of heat that can be converted to mechanical energy
depends on the intake and exhaust temperatures
In any process the maximum amount of mechanical energy that can be conveted to heat
A frictionless heat engine can be 100% efficient only if its exhaust temperature is
The physics of a refridgerator most closely resembles the physics of
a heat engine
The working substance used in most refridgerators in a
gas that is easy to liquify
Heat is absorbed by the refrigeratn in a refridgerator when it
The heat a refridgerator absorbs from its contents is
less than it gives off
The seconmd law of thermodynamics does not lead to the conclusion that
the total amopunt of energy in the universe including rest energy is constant
The greater the entropy of a system of particles
the less the order of the system
ethyl alcohol boils at 172 degrees F. The celsius equivalent of this temperature is
78 degrees C
A temperature of 20 degrees C is the same as
68 degrees F
The heat needed to warm 8 kg of water from 20 degress to 70 degrees C is
When 1 kg of steam at 20 degrees C loses 3 MJ of heat, the result is
water and ice
A 40 concrete block has the dimensions 1m 0.6 m 0.3 m. Its density is
An object suspended from a spring scale is lowered into a pail filledd to the brim with water; and 4 N of water overflows. The scale shows that the object weighs 6 N in the water. The weight in air of the object is
Lead melts at 330 degrees C. On the absolute scale this temperature corresponds to
At which of the following temperatures would the molecules of a gas have twice the average kinetic energy they have at room temperature, 20 degrees C
313 degrees C
A heat engine absorbs heat at a temperature of 127 degrees C and exhausts heat at a temperature of 77 degrees C. Its maximum efficiency is
occurs only in seperate parcles of +/- 1.6 * 10^-19 C
A negative electric charge
interacts with both positive and negative charges
A positively charged rod is brought near an isolated metal ball. Which of the sketches best illustrates the arrangement of charges on the ball?
Which of the following statements is notr true?
protons and electrons have equal masses
Coulumb's Law for the force between electric charges belongs in the same category as
Newtons law of gravitation
The electric force between a proton and an electron
is stronger than the gravitiational force between them
The electrons in an atom
are some distance away from the nucleus
Atoms and molecules are normally
An object has a postive electric charge whenever
moving electrons constitute an electric current
superconductivity occurs in certain substance
only at very low temperautres
electric power is equal to
current * voltage
the electric energy lost when a current passes
when a magnetized bar of iron is strongly heated, its magnetization
All magnetic fields originate in
moving electric charges
The force on an electron that moves in a curvd path must be
one or more of these
a drawing of the field lines of magnitude field provides information on
both the direcion and the strength of the field
magnetic field lines provide convenient way to visualize a magnetic field. Which of the following statements is not true?
the path followed by an electric charge released near a magent corresponds to a field line
A moving electric charge produces
both an electric and magnetic field
the magnetic field of a bar magnet resembles most closely the magnetic field of
a wore loop carrying a direct current
the magnetic field shown in fig 6-51 is produced by
two south poles
the magnetic field lines around a long straight current are
concentric circles around the current
A magent does not exert a force on
a stationary electric charge
a current carrying wire is in a magnetic field with the direction of the current the same as that of the field
the wire has no tendency to move or to turn
uses an electric current to produce a magnetic field
The nature of the force that is responsible for the operation of an electric motor is
A generator is said to "generate electricity." What it actually does is act as a source of