Exam #4 homework
What change in atomic number occurs when a nucleus emits an alpha particle? A beta particle? A gamma ray?
-2, +1, 0
Two charges separated by one meter exert 1-N forces on each other. If the charges are pulled 3 meters apart, the force on each charge will be
0.11 N
A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed it would have hit the ground in
0.5 s
A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 second later?
100 m
The half-life of carbon 14 is 5730 years. If a 1-gram sample of old carbon is 1/8 as radioactive as 1-gram of a current sample, then the age of the old sample is about
17,200 years
A certain radioactive isotope placed near a Geiger counter registers 160 counts per minute. Eight hours later, the counter registers 10 counts per minute. What is the half-life of the isotope?
2 hours
A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation 5 m above ground level. The ball lands 20 m downrange. The player's pitching speed is about
20 m/s
Two charges that are separated by one meter exert 1-N forces on each other. If the magnitude of each charge is doubled, the force on each charge is
4 N
If you throw a stone horizontally from the top of a cliff, one second after leaving your hand its vertical distance below the top of the cliff is
5 m
A projectile falls beneath the straight-line path it would follow if there were no gravity. How many meters does it fall below this line if it has been traveling for 1 s? For 2 s?
5 m, 20 m
About how far below a straight-line path does a satellite in close Earth orbit fall in the first second of fall?
5 meters
How far below a straight-line path does a horizontally projected projectile fall in the first second of fall?
5 meters
When thorium (atomic number 90) decays by emitting an alpha particle, what is the atomic number of the resulting nucleus?
88
How much time does it take for a complete revolution of a satellite in close orbit about Earth?
90 minutes
When thorium decays by emitting a beta particle, what is the atomic number of the resulting nucleus?
91
Who first explained Brownian motion and made a convincing case for the existence of atoms?
Albert Einstein
Who gathered the data that showed planets traveling in elliptical paths around the Sun? Who discovered elliptical orbits? Who explained them?
Brahe, Kepler, Newton
Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be
F/2
Who advanced the idea of atoms in the early 1800s?
John Dalton
Who envisioned the motion of planets as projectiles obeying the laws of physics?
Newton
How is Coulomb's law similar to Newton's law of gravitation? How is it different?
Newton's law of gravitation is attractive, whereas Coulomb's law is attractive or repulsive. Both are proportional to the inverse square of distance
What two elements did Pierre and Marie Curie discover?
Polonium and radium
Which investigator is credited for discovering Brownian motion?
Robert Brown
What is a positive ion? What is a negative ion?
a positive ion is a neutral atom that lost one or more electrons. A negative ion is a neutral atom that has gained one or more electrons
For 1 gram of radioactive material that has a half-life of one year, after 4 years the original radioactive material left will be
a) 1/2 g b) 1/8 g c) 1/4 g d) o g e) none of the above (CORRECT)
When thorium (A = 90) emits a beta particle, the resulting nucleus has atomic number
a) 90 b) 88 c) 92 d) 89 e) none of the above (CORRECT)
Which of these is electromagnetic radiation?
a) Gamma radiation (CORRECT) b) Alpha radiation c) Debris of nuclear decay d) Beta radiation
Which of these investigators did NOT contribute to our knowledge of atoms?
a) John Dalton b) Aristotle (CORRECT) c) Albert Einstein d) Robert Brown
Which of the following are negatively charged?
a) atomic nuclei b) neutrons c) protons d) electrons (CORRECT)
An element that undergoes radioactive decay becomes _________.
an entirely different element
Nuclei of atoms that make up a newborn baby were manufactured in
ancient stars
According to Kepler's second law, as a planet or other object moves around its orbit, it sweeps out equal __________ in equal __________.
areas /times
A bullet fired horizontally from a rifle begins to fall
as soon as it leaves the barrel
Earth satellites are typically more than 100 km high so as to be above Earth's
atmosphere
An electron and a proton
attract each other
A ball rolls off the edge of a table at the same time another ball drops vertically from the same table. The ball to hit the floor first is the
both hit at the same time
It is said that electric charge is conserved, which means that electric charge
can be neither created nor destroyed
The electrical force between charges is strongest when the charges are
close together
What causes dust particles and tiny grains of soot to move with Brownian motion?
collisions with invisible molecules
How far does the bullet drop from a straight-line horizontal path by the time it reaches the target
d= 2.28 m
What kind of attraction pulls electrons close to the atomic nucleus?
electric
The force that binds atoms together to form molecules is
electrical
Kepler was the first to be credited for discovering that planets follow __________.
elliptical paths
Consider two triangles that represent the swept-out area in some time period as an object orbits the Sun. If one triangle is short and squat (where the object is close to the Sun) and the other is long and thin (where the object is far from the Sun), then the object must have moved __________.
farther in the case where the triangle is short an squat
According to Kepler, the speed of a planet is slowest when it is
farthest from the Sun
To become a negative ion, an atom must
gain an electron
Which radiation has no association with electric charge?
gamma
Which will NOT bend when moving in a magnetic field?
gamma ray
An isotope is simply an atom that
has different numbers of neutrons for the same element
One neutron added to a helium nucleus results in
helium
When the hydrogen isotope tritium-3 emits a beta particle, it becomes an isotope of
helium
Where in the atom is most of its mass concentrated? What is this mass composed of?
in the nucleus as protons and neutrons
When a nucleus emits a beta particle, its atomic number
increases by 1
The horizontal and vertical components of velocity for a projectile are __________.
independent of each other
Are most of the atoms around us younger or older than the Sun?
most are older than the Sun
According to Kepler's second law, planets and other objects orbiting the Sun move fastest when they are __________.
nearest to the Sun
According to Kepler's second law, planets or other objects orbiting the Sun move fastest when they are __________.
nearest to the Sun
A ball rolled along a horizontal surface maintains a constant speed because
no horizontal force acts on it
How are most of the elements with nuclei heavier than those of hydrogen and helium formed?
nuclear fission in stars
Mass number refers to the number of
nucleons in the nucleus
For an isotope with a half-life of one day, at the end of three days the amount that remains is
one-eighth
If a certain isotope has a radioactive half-life of 10 years, how much of the isotope will remain at the end of 20 years?
one-quarter
Two charged particles held a certain distance apart are released. As they move, the force on each particle increases. Therefore, their charges have
opposite signs
The number of protons in a neutral atom is balanced by an equal number of
orbital electrons
Brownian motion is caused by
particles larger than atoms bumping into them
For an Earth satellite in an elliptical orbit, list all the values that do change.
speed, gravitational force, and distance from Earth
Which part of an atom is positively charged, and which part is negatively charged?
the nucleus is positively charged and the electron cloud is negatively charged
What does the atomic number of an element tell you about the element?
the number of protons in its nucleus
How does the approximate number of atoms in the air in your lungs compare with the number of breaths of air in Earth's atmosphere?
the numbers are about the same, 10^23
Why are metals good conductors of both heat and electricity?
the outer shell electrons in metals are free to move from atom to atom
What did Kepler discover about the periods of planets and their distances from the Sun?
the period squared was proportional to the distance cubed
How does the rate of decay of a long-half-life material normally compare to the rate of decay of a short-half-life material?
the rate of decay is lower for a long half-life material
Dr. Chuck projects a ball horizontally from a lab bench. If the projection speed of the ball were greater, the time in the air would be
the same
Dr. Chuck projects a ball horizontally from a lab bench. The ball lands on a bullseye marked on the floor a horizontal distance away. Compared to the time for the ball to simply drop vertically from the bench, the time in the air for Dr. Chuck's projected ball is
the same
Particle A has twice the charge of nearby particle B. Compared to the force on Particle A, the force on Particle B is
the same
Nellie tosses a ball upward at an angle. Assuming no air resistance, which component of velocity changes with time?
the vertical component
There are about as many atoms of air in our lungs at any moment as there are breaths of air in the atmosphere of
the whole world
Which is more prevalent in the food we eat: carbon-12 or carbon-14?
there is about one carbon-14 atom for every 100 billion carbon-12 atoms
Most atoms normally have a net charge that is _________.
zero
How can a projectile "fall around the Earth"?
a) a projectile can "fall around Earth" if the distance it falls matches the curvature of Earth. b) the projectile falls 5 m for every 8 km and so does Earth. c) in a circular orbit around a spherical planet, the force and the fall are always toward the center. d) all of the above (CORRECT)
In which of these processes is an element transformed into a completely different element?
a) beta decay b) alpha decay c) both of these (CORRECT) d) none of these
Electrostatics is a branch of electricity that focuses on
a) electrical force b) both of these when static (CORRECT) c) electrical charges d) none of the above
Which of these does NOT have an electrical charge?
a) electron b) proton c) neutron (CORRECT) d) all of the above e) none of the above
Which of these will penetrate into lead?
a) gamma ray (CORRECT) b) alpha particle c) beta particle d) all of the above
It takes Neptune a longer time to orbit the Sun than Earth does because Neptune
a) goes much slower b) has much further to go c) both of these (CORRECT) d) none of these
Which of the following elements has the most mass?
a) lead b) uranium (CORRECT) c) hydrogen d) iron e) all have the same mass
A fundamental rule of electricity is that
a) like kinds of charges repel b) unlike charges attract c) both of these (CORRECT) d) neither of these
Which is the lightest particle?
a) neutron b) electron (CORRECT) c) proton d) all about the same
The focal point of a satellite in orbit about the Sun is
a) outside the Sun b) inside the Sun c) both of these (CORRECT) d) neither of these
Which of these has the greatest number of protons in its nucleus?
a) silver b) gold c) lead (CORRECT) d) mercury
Suppose two cars both drive for one hour. Which statement is true?
a) they both go the same distance b) the one that goes faster travels farther (TRUE) c) the one that goes slower travels farther
How does the charge of one electron compare to that of another electron? How does it compare with the charge of a proton? How do the masses of protons and electrons compare?
all electrons have the same charge. Electron charge is equal and opposite to the proton charge. A proton has 1800 times the mass of an electron
In a smoke detector americium (A = 95) transmutes to neptunium (A = 93) by
alpha emission
What is the change in the atomic mass number for each of the reactions in the preceding two questions
alpha emission -2, beta emissions 0
What kind of rays are X-rays?
electromagnetic
The chemical properties of matter are due mostly to their
electrons
Why are materials such as glass and rubber good insulators?
electrons are tightly bound to their atoms, making them poor conductors of heat
In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus
What happens to electrons in any charging process?
electrons transfer from one place to another
When an element undergoes nuclear transmutation, the result is a completely different
element
How does one isotope differ from another?
it has a different number of neutrons
How does the electric charge of a proton compare with the electric charge of an electron?
it is equal and opposite
As soon as a ball rolls off the edge of a table
it is not acted on by any horizontal forces
The Early Bird communication satellite hovers over the same point on Earth's equator indefinitely, because
its orbital period is 24 hours
A weightless astronaut in an orbiting satellite is
like the satellite, pulled by Earth's gravitation
Compared with the period of satellites in close Earth orbit, the period of satellites orbiting far from Earth is
longer
Charge carriers in a metal are electrons rather than protons because electrons are
loosely bound
Name the two different nucleons.
proton and neutron
The mass of matter is due mostly to its
protons
Atomic number refers to the number of
protons in the nucleus
When the distance between two charges is halved, the electrical force between them
quadruples
What did Robert Brown see in his microscope?
random motions
As soon as a bowling ball rolls off the edge of a table its horizontal component of velocity
remains constant
A stone is thrown upward at an angle. What happens to the horizontal component of its velocity as it rises? As it falls?
rising or falling, it does not change
Newton hypothesized that the forces acting on planets was
toward the Sun
