Physics Test #3
it is more likely in trial A
A ball is suspended by a string that is tied to a fixed point above a wooden block standing on end. The ball is pulled back as shown in the figure below and released. In trial A, the ball rebounds elastically from the block. In trial B, two-sided tape causes the ball to stick to the block. In which case is the ball more likely to knock the block over?
the ball plus earth
A basketball is tossed up into the air, falls freely, and bounces from the wooden floor. From the moment after the player releases it until the ball reaches the top of its bounce, what is the smallest system for which momentum is conserved?
the basketball
A basketball rolls across a classroom floor without slipping, with its center of mass moving at a certain speed. A block of ice of the same mass is set sliding across the floor with the same speed along a parallel line. Which object has more kinetic energy?
yes
A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider only the process of the boxcar gaining speed as it rolls down the hump. Consider the boxcar and the Earth as a system. Is mechanical energy of this system conserved?
yes
A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider only the process of the boxcar gaining speed as it rolls down the hump. Consider the boxcar and the Earth as a system. Is momentum of this system conserved?
no
A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider the two cars as a system as the boxcar is slowing down in the coupling process. Is mechanical energy of this system conserved?
yes
A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider the two cars as a system as the boxcar is slowing down in the coupling process. Is momentum of this system conserved?
no
A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider the two cars as a system from the moment of release of the boxcar until both are rolling together. Is mechanical energy of the system conserved?
no
A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider the two cars as a system from the moment of release of the boxcar until both are rolling together. Is the momentum of the system conserved?
kinetic energy, angular position and angular velocity
A constant net torque is exerted on an object. Which quantities for the object cannot be constant?
their momentum changes are the same size
A massive tractor rolls down a country road. In a perfectly inelastic collision, a small sports car runs into the machine from behind. Which vehicle experiences a change in momentum of larger magnitude?
the car
A massive tractor rolls down a country road. In a perfectly inelastic collision, a small sports car runs into the machine from behind. Which vehicle experiences a larger change in kinetic energy?
a slight increase
A person shakes a sealed insulated bottle containing hot coffee for a few minutes. What is the change in the internal energy of the coffee?
a slight increase
A person shakes a sealed insulated bottle containing hot coffee for a few minutes. What is the change in the temperature of the coffee?
high specific heat and low thermal conductivity
A poker is a stiff, nonflammable rod used to push burning logs around in a fireplace. For safety and comfort of use, the poker should be made from a material with which properties?
zero
A toy airplane hangs from the ceiling at the bottom end of a string. You turn the airplane many times to wind up the string clockwise and release it. The airplane starts to spin counterclockwise, slowly at first and then faster and faster. Take counterclockwise as the positive sense and assume friction is negligible. When the string is entirely unwound, the airplane has its maximum rate of rotation. At this moment, its angular acceleration is (positive/negative/zero).
negative
A toy airplane hangs from the ceiling at the bottom end of a string. You turn the airplane many times to wind up the string clockwise and release it. The airplane starts to spin counterclockwise, slowly at first and then faster and faster. Take counterclockwise as the positive sense and assume friction is negligible. When the string is entirely unwound, the airplane has its maximum rate of rotation. The airplane continues to spin, winding the string counterclockwise as it slows down. At the moment it momentarily stops, is its angular acceleration is (positive/negative/zero).
the specific heat of ice is less than that of water
An amount of energy is added to ice, raising its temperature from -10°C to -5°C. A larger amount of energy is added to the same mass of water, raising its temperature from 15°C to 20°C. From these results, what can we conclude?
adiabatic
An ideal gas is compressed to half its initial volume by means of several possible processes. Which of the following processes results in the most work done on the gas?
the internal energy of the gas remains constant
If a gas is compressed isothermally, which of the following statements is true?
work is done on or by the gas
If a gas undergoes an isobaric process, which of the following statements is true?
on
If an ideal gas undergoes adiabatic expansion, negative work is done (by/on) the gas.
decreases
If an ideal gas undergoes adiabatic expansion, the internal energy of the gas _____.
decreases
If an ideal gas undergoes adiabatic expansion, the temperature of the gas _____.
is not
If an ideal gas undergoes adiabatic expansion, there (is/is not) thermal energy transferred to the gas.
energy, momentum and angular momentum
If any collection of particles is isolated, 3 independent conservation laws that apply to the collection are conservation of _____, _____ and _____.
the pressure increases by a factor of 2
If the volume of an ideal gas is doubled while its temperature is quadrupled, what happens to the pressure?
angular momentum/velocity
If there's zero net external torque on an object (about an axis), then the _____ _____ is constant in time about that axis.
yes, if both their masses and directions of motion are the same
If two particles have equal kinetic energies, are their momenta equal?
no, except when their speeds are the same
If two particles have equal momenta, are their kinetic energies equal?
energy
The 1st Law of Thermodynamics is a special case of conservation of _____.
rotational inertia
The _____ _____ is a measure of resistance to changing angular velocity.
net torque
The angular acceleration of a rigid body is directly proportional to the _____ _____ rigid body.
momentum
The time rate of change of the _____ is equal to the net force on an object.
the pressure in A is 1/3 the pressure in B
Two cylinders A and B at the same temperature contain the same quantity of the same kind of gas. Cylinder A has three times the volume of cylinder B. What can you conclude about the pressures the gases exert?
the particle of larger mass has more momentum
Two particles of different mass start from rest. The same net force (Fnet ≠ 0) acts on both of them as they move over equal distances. How do the magnitudes of their final momenta compare?
the particles have equal kinetic energies
Two particles of different mass start from rest. The same net force acts on both of them as they move over equal distances. How do their final kinetic energies compare?
no energy is delivered to the gas by heat
When an ideal gas undergoes an adiabatic expansion, which of the following statements is true?
the basketball
its center of mass moving at a certain speed. A block of ice of the same mass is set sliding across the floor with the same speed along a parallel line. The two objects encounter a ramp sloping upward. Which object will travel farther up the ramp?
they have equal momentum
its center of mass moving at a certain speed. A block of ice of the same mass is set sliding across the floor with the same speed along a parallel line. Which object has more momentum?
