Physics Final 103
Wave motion in a material medium involves
- interparticle interactions. - the propagation of a disturbance. - the transfer of energy.
Angular kinematics and linear kinematics are analogous. Which of the following sets of analogies is correct?
- theta plays a similar role to x (position) - omega plays a similar role to v (velocity) - alpha plays a similar role to a (acceleration)
The maximum speed of an object in simple harmonic motion:
-depends on the angular frequency. -depends on the amplitude.
A wheel has a radius of 0.5 m and rotates with an angular speed of 0.5 rad/s. If the wheel rolls without slipping, what is the center-of-mass speed?
0.25 m/s
A container is filled with oil and fitted on both ends with pistons. The area of the left piston is 10 mm-squared; that of the right piston is 10,000 mm-squared. What force must be exerted on the left piston to keep the 10,000 N car on the right at the same height?
10 N
A mass of 1.00 kg is attached to a spring with spring constant 100 N/m. Which of the following is the angular frequency of the motion the mass will undergo?
10.0 rad/s
If the intensity of a sound is one million times larger than the threshold of hearing, then the sound intensity level in decibels is
60 dB
Two cylinders, with the same size and mass, roll down an incline. The cylinders begin at the same height on the incline. Cylinder A has most of its mass concentrated at the rim, while cylinder B has most of its mass concentrated at the center. Which reaches the bottom of the incline first?
B
Jack and Jill are both moving with the same velocity (same speed in the same direction). A stationary sound source is between them so that Jack is moving away from the source and Jill is moving towards it. Which of the following is correct?
Compared to the emitted frequency, Jack hears a lower frequency and Jill hears a higher frequency.
Two bicyclists are riding together, each with the same speed. Cyclist A's bike has tires that are smaller than those on cyclist B's bike. As long as the tires are rolling without slipping, which of the following must be true?
Cyclist A is pedaling harder than B, so that her tires have larger ω.
Two identical masses are attached to two identical springs so that each mass oscillates simple harmonically. Mass A is pulled a distance x from equilibrium; mass B is pulled a distance 4x. Which of the following correctly links the energies of the two masses?
EA = (1/16)EB, since B is pulled 4 times farther.
An object moves in a circular path with a constant speed. It does not experience any acceleration. (T/F)
False
An object moves with simple harmonic motion only if the object is a mass attached to a spring. (T/F)
False
During a collision between a hockey puck and a hockey stick laying on the ice, the angular momentum of the hockey puck must remain constant. (T/F)
False
In a pendulum, tension is the restoring force. (T/F)
False
When using an intravenous injection (IV) system to deliver medication to patients, the patient's blood pressure is unimportant. (T/F)
False
When you use a wrench to loosen or tighten a bolt, the entire force that you apply to the wrench causes a torque. (T/F)
False
In a lab, you have 4 identical pipes - same lengths and diameters. You also have reservoirs of the following 4 liquids: honey, glycerine, motor oil, and water. You can attach the reservoirs to the pipes and make the liquids flow by creating pressure differences between the ends of the pipes. For a fixed pressure difference of 10 kPa, which of the liquids will have the SMALLEST flow speed?
Honey
You have 4 identical 10 kg masses. Two of the masses are connected by a very light bar with length 1 m, and the other two are connected by another very light bar with length 1.5 m. Call the short barbell A and the long barbell B. Which of the following statements is correct?
It will be easier to start A rotating than B.
During a track meet around a circular track, two runners must stay in lanes with different radii. Julie's lane has a radius that is half as big as Joe's lane - Julie is closer to the center than Joe. If Julie and Joe both run with the same constant speed, then
Julie will complete one lap in half the time that it takes Joe to complete one lap.
Which pipe requires a greater pressure difference to make a given fluid flow through it with speed v: pipe 1 with L = 1 m and a diameter of 0.2 m, or pipe 2 with L = 2 m and a diameter of 0.1 m?
Pipe 2
A student can apply a torque of 15 N-m to every door (which acts like a thin rectangular sheet) she encounters. To enter a building, the student must open an outer door with a mass of 25 kg. Once inside, she must open an inner door of identical size, but the mass is only 10 kg. Which of the following is true?
The angular acceleration of the inner door is larger than the angular acceleration of the outer door.
A passenger car that has tires with radius = 0.3 m travels along a highway. The car pulls alongside a tractor-trailer that has tires with radius = 0.6 m and moves with the same velocity. If the tires roll without slipping, which of the following statements is correct?
The angular speed of the car's tires is larger than the angular speed of the tractor's tires.
You have two solid cubes of material. The cubes are not the same size. When you put them in a container with water, one floats and the other sinks. Which of the following statements is true?
The density of the object that sinks must be larger than the density of the object that floats.
On the first Tuesday of every month a town tests its tornado alarm system. Each alarm produces a single-wavelength tone. A resident finds that standing in a particular spot significantly reduces the volume of the alarms. Which of the following must be true for this to occur?
The distances between the resident and the alarms must be different by some number of half-wavelengths of the tone.
A hockey puck slides along an icy surface and hits a stick laying on the ice. What system can conserve angular momentum?
The hockey puck and the stick together since their interaction forces are equal and opposite.
In a lab, you are experimenting with two springs - spring A is stiff (has a large k), spring B is soft (has a small k). Spring A has a length that is twice that of spring B. If you hang an identical mass on each spring and give them the same initial displacement, which of the following is correct?
The mass on spring A will have a shorter period of oscillation than the mass on spring B, but the amplitudes of their motions will be equal.
A vertical tube of water has the same radius and height as a vertical tube of mercury. Mercury has a larger density than water. Which tube has the larger pressure at the bottom?
The mercury tube because it has the larger mass.
A child sits at the center of a rotating merry-go-round. She slides to the edge and then returns to the center. Which of the following is correct (assume negligible friction in the merry-go-round bearings)?
The merry-go-round slows down, then speeds up to its original angular speed.
Two identical masses (A and B) are attached to strings and spun in vertical circular paths. The string attached to mass A is twice as long as the string attached to mass B. Which of the following is correct?
The minimum speed necessary to maintain circular motion for mass A is about 40% larger than for mass B.
A common carnival ride involves a large cylindrical drum that rotates at high speed. Riders stand along the inner surface of the drum, and when it rotates they become "stuck" to the wall. Which of the following is correct?
The normal force from the wall provides the centripetal force.
As you sit on your front porch, a fire truck drives down the street towards your house. The fire truck has a siren that emits a continuous sound. Which of the following situations correctly describes the sound wave that you hear?
The observed sound wave has a shorter wavelength and higher frequency than the wave emitted by the siren.
A single particle is a distance r from an axis of rotation. If the particle is moved to a distance 2r, which of the following correctly describes the change in the moment of inertia?
The particle's moment of inertia about that axis of rotation increases by a factor of 4.
A vertical tube of water has the same radius and mass as a vertical tube of mercury. Mercury has a larger density than water. Which tube has the larger pressure at the bottom?
The tubes have the same pressure because they have the same mass.
Light waves are special kinds of transverse waves that always have the same speed (in vacuum). Given this, how does the wavelength of higher-frequency blue light compare to the wavelength of lower frequency red light?
The wavelength of red light is LONGER than the wavelength of blue light.
A rigid body is spinning with a constant angular speed. As you observe it, this speed decreases, but the body remains unchanged. What can you infer?
There must be some external force exerting a torque.
What does oscillate mean?
To move in a continuous motion
A ball is attached to a rope and swung in a vertical circle. As the speed of the ball at the top of the circle increases, so too does the tension in the rope. (T/F)
True
A ball is attached to a rope and swung in a vertical circle. The ball is not in uniform circular motion due to the acceleration due to gravity. (T/F)
True
A ball is attached to a rope and swung in a vertical circle. The speed of the ball changes most rapidly when the ball is halfway between the top and the bottom. (T/F)
True
A hockey puck has a perfectly inelastic collision with a stick laying on the ice. The angular momentum of the system must be conserved because there is no net external torque, but the kinetic energy must decrease. (T/F)
True
A race car travels around a circular track. As it moves, it increases its speed around the track. In this case, the centripetal acceleration experienced by the car is a vector that points directly at the center of the track. (T/F)
True
If an object conserves angular momentum, it can only change is angular speed if its moment of inertia changes as well.
True
If wave A and wave B have the same period, but A's wavelength is twice that of B, then wave A has to move a twice the speed of B. (T/F)
True
The acceleration of an object in simple harmonic motion always has a sign opposite from the sign of the position. For example, a mass with positive position must experience a negative acceleration. (T/F)
True
Two identical objects can have different moments of inertia depending on how they rotate.
True
In a lab, you have 4 identical pipes - same lengths and diameters. You also have reservoirs of the following 4 liquids: honey, glycerine, motor oil, and water. You can attach the reservoirs to the pipes and make the liquids flow by creating pressure differences between the ends of the pipes. Which liquid will require the SMALLEST pressure difference to flow at 1 m/s through the pipes?
Water
You are driving a car around a circular track. Which of the following statements are true?
Your angular momentum will increase if you increase your tangential speed.
For translational motion of a rigid body,
all constituent particles of the body share the same velocity as the center-of-mass.
A solid disk and a ring roll down an incline. The ring is slower than the disk
always. The ring is always slower regardless of the relative values of the mass or radius.
A blood platelet drifts along with the flow of blood through an artery that is partially blocked by deposits. As the platelet moves from the narrow region to the wider region, it experiences
an increases in pressure.
A cylindrical tube is completely filled with fluid. If the tube is squeezed so that the radius decreases, then
both the density and pressure of the fluid increase.
Water waves with large amplitudes (like those that form tsunamis)
can move faster or slower than waves with smaller amplitudes.
When pulleys have significant mass, the tension in the string that passes over them
changes as you move around the pulley
A blood platelet drifts along with the flow of blood through an artery that is partially blocked by deposits. As the platelet moves from the narrow region to the wider region, its speed
decreases
A blood platelet drifts along with the flow of blood through an artery that is partially blocked by deposits. As the platelet moves from the narrow region to the wider region, its speed Correct Answer
decreases.
Hearing people talking around a corner of a building is an example of:
diffraction
When describing the rotational motion of a rigid body
every particle in the body has to move with the same angular speed.
The figure above shows the wavefronts generated by an airplane flying past an observer A at a speed greater than that of sound. After the airplane has passed, the observer reports hearing
first nothing, then a sonic boom, then the sound of engines.
A ball is attached to a rope and swung in a vertical circle. The tension in the rope
has a larger magnitude when the ball is at the top of the circle than when it is at the bottom.
Imagine you are standing along a street waiting for a friend to pick you up. A car passes you while the driver blasts his horn. The frequency of the sound you hear is
higher than the emitted frequency as the car approaches and lower than the emitted frequency as the car moves away.
Imagine you have a choice to A) double the radius of a solid sphere, or B) double its angular speed. The rotational kinetic energy of the sphere
increases by the same amount for A and B.
Beats are a direct result of
interference
The total mechanical energy of an object in simple harmonic motion
is constant
A ball is attached to a rope and is swung in a vertical circle. The centripetal force
is due to a combination of the tension in the rope and gravity.
A sound wave in air
is longitudinal
A force acts on an object causing a torque (so the object will move along a circular path). The only component of the force that does work
is the component that is tangential to the circular path.
A string is clamped at both ends and plucked so it vibrates in a standing mode between the two extreme positions a and b shown in the figure. Let upward motion correspond to positive velocities. When the string is in position b, the instantaneous velocity of points along the string
is zero everywhere.
A ball is attached to a rope and swung in a vertical circle. When the ball has the same height as the center of the circle (midway between the top and bottom),
it experiences its greatest tangential acceleration.
The best model of solar system formation is that a giant spherical gas cloud shrinks (its radius gets smaller), forming a central star. The cloud does not have any nearby neighbors that can exert forces on it. If the gas cloud is slowly rotating in its initial, large radius state,
it must rotate faster after it shrinks.
bservers A & B hear sounds from a source that is at rest. Observer A is moving towards the source, and observer B is at rest with respect to the source. Observer A
measures the same wavelength as observer B but a larger wave speed.
In a simple pendulum, the magnitude of the force that causes simple harmonic motion is
mg sinθ.
Consider an object that floats in water but sinks in oil. When the object floats in water, half of it is submerged. If we slowly pour oil on top of the water so it completely covers the object, the object
moves upwards.
The kinetic energy of an object that rolls without slipping
must have contributions from its translational and rotational motions.
When a REAL fluid flows through a pipe/tube, the flow velocity is
near-zero along the walls and largest near at the center of the pipe/tube.
Object A has triple the mass of object B. Object A is attached to a cable that hangs from the ceiling in a room. If object B is attached to an identical cable in the same room, then
object A will oscillate with the same frequency as object B.
Your friend is yelling to you across a parking lot. You expect the sound to reach you fastest
on a hot, humid day.
For a longitudinal wave, the direction between the wave velocity and particle oscillation is
parallel.
Constructive and destructive interference of sound waves depends on
phase difference
The distance covered by an object that undergoes a 90 degree change in angular position is
pi/2 times the radial distance of the object
A grandfather clock depends on the period of a pendulum to keep correct time. Suppose a grandfather clock is calibrated correctly and then a mischevious child slides the bob of the pendulum down on the oscillating rod. Does the grandfather clock now run
slow (fewer ticks per second compared to initial).
The speed of sound is generally greatest in
solids
A basketball (a thin spherical shell) and a solid plastic ball have the same mass and radius. If they are both spun about an axis along their diameters with the same angular speed,
the basketball has more kinetic energy.
If a torque does negative work on an object,
the final angular speed of the object is smaller than the initial angular speed of the object.
Imagine you are giving someone a shot with a hypodermic needle. As you push the plunger down, you are applying a force to the liquid in the reservoir. According to Pascal's principle, since the needle opening is much smaller than the reservoir radius,
the force at the needle opening is much smaller than the force you exerted on the plunger.
Two people and a dog are in a park. Jack is 10 m from the dog and Polly is 20 m away from the dog. When the dog barks,
the intensity of the sound at Jack's position is 4-times larger than at Polly's position.
A child sits at the center of a rotating merry-go-round. If she slides towards the edge,
the kinetic energy of the system must decrease.
A child sits at the center of a rotating merry-go-round. If she slides towards the edge,
the merry-go-round should slow down.
A thin rod rotates about one end with a constant angular acceleration of 0.1 rad/s^2. If the rod is modified to rotate about its mid-point with an angular acceleration of 0.1 rad/s^2,
the net torque on the rod is smaller when it rotates about its mid-point.
On a chopper style motorcycle, the front wheel is one-half the size of the rear wheel. If each wheel turns with the same speed,
the rear wheel experiences a centripetal acceleration that is one-half that of the front wheel.
When an IDEAL fluid flows through a pipe/tube, the flow velocity is
the same across the cross-sectional area of the pipe/tube.
Imagine you are designing a vertical spinning wheel for a game show. Contestants will grab the wheel at its edge, apply a force tangent to the wheel, and watch it spin. You make two prototype wheels with the same mass and radius, but one is a solid disk while the other is a hoop. For a given contestant's applied force,
the solid disk will have a larger angular acceleration.
Viscosity describes
the tendency of a fluid to resist flow.
Two identical glasses are filled to the same level with water. One of the two glasses has ice cubes floating in it. Which weighs more?
the two glasses weigh the same.
Surface tension exists in real liquids because
the weak intermolecular forces of interior molecules provide a net inward force for surface molecules.
Buoyant forces occur because
there is a pressure difference across an object in a fluid.
As a car drives around a circular track at a constant speed, the acceleration vector points
towards the center of the circular track always.
Two solid disks rotate with the same angular speed. Disk A has a radius that is twice as large as Disk B. Compared to a point at the edge of Disk B, a point at the edge of Disk A
will have twice the centripetal acceleration and linear speed.
As you enter a store, a turnstile bar must be rotated out of the way. One end of the bar is attached to a rotating hub, while the other is free. To minimize the amount of force that must be applied,
you should push as close to the free end of the bar as possible.
A bucket of water is swung around in a vertical circle in such a way that the tension in the rope disappears when the bucket is exactly overhead. The normal force exerted by the bucket on the water at this point is
zero
