Physics Exam 3 Conceptuals
If a guitar string has a fundamental frequency of 500 Hz, which one of the following frequencies can set the string into resonant vibration?
1500 Hz
A rubber band is stretched by 1.0 cm when a force of 0.35 N is applied to each end. If instead a force of 0.70 N is applied to each end, estimate how far the rubber band will stretch from its unstretched length:
2 cm
A tiger is running in a straight line. If we double both the mass and speed of the tiger, the magnitude of its momentum will increase by what factor?
4
A styrofoam sphere of radius R has a density ρ. You now carefully compress the sphere so its radius is R/2. What is the density of the compressed sphere?
8 ρ
As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?
90 degree angle
A total mechanical energy of a simple harmonic oscillating system is
A non zero constant
Three containers are filled with water to the same height and have the same surface area at the base, but the total weight of water is different for each. In which container does the water exert the greatest force on the bottom of the container?
All three are equal.
A mass on the end of a spring undergoes simple harmonic motion. At the instant when the mass is at its equilibrium position, what is its instantaneous velocity?
At equilibrium, its instantaneous velocity is at maximum.
Consider a uniform hoop of radius R and mass M rolling without slipping. Which is larger, its translational kinetic energy or its rotational kinetic energy?
Both are equal
At a playground, two young children are on identical swings. One child appears to be about twice as heavy as the other. If you pull them back together the same distance and release them to start them swinging, what will you notice about the oscillations of the two children?
Both children swing with the same period.
Consider a wave traveling down a cord and the transverse motion of a small piece of the cord. Which of the following is true?
Both the frequency and the amplitude of the wave must be the same as the frequency and the amplitude of a small piece of the cord.
You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You have two choices about what to do with the ball: either catch the ball or deflect it back toward your friend with the same speed as it was originally thrown. Which choice should you make in order to maximize your speed on the skateboard?
Deflect the ball back.
When a heavy metal block is supported by a cylindrical vertical post of radius R, it exerts a force F on the post. If the diameter of the post is increased to 2R, what force does the block now exert on the post?
F
If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero.
FALSE
The boat in the water holds an iron anchor which is removed from the boat and placed on the shore. The level of the water will
Fall
The boat is removed from the water. The level of the water will
Fall
A heavy ball suspended by a cable is pulled to the side by a horizontal force F If angle θ is small, the magnitude of the force F can be less than the weight of the ball because:
F⃗ is equal to only the x component of the tension in the cable.
A parking garage is designed for two levels of cars. To make more money, the owner decides to double the size of the garage in each dimension (length, width, and number of levels). For the support columns to hold up four floors instead of two, how should he change the columns' diameter?
Increase the area of the columns by a factor of 8 by increasing their diameter by a factor of 2√2
A student attaches one end of a Slinky to the top of a table. She holds the other end in her hand, stretches it to a length ℓ, and then moves it back and forth to send a wave down the Slinky. If she next moves her hand faster while keeping the length of the Slinky the same, how does the wavelength down the Slinky change?
It decreases.
A small mass m on a string is rotating without friction in a circle. The string is shortened by pulling it through the axis of rotation without any external torque What happens to the angular velocity of the object?
It increases
A cubical block of stone is lowered at a steady rate into the ocean by a crane always keeping the bottom faces horizontal. Which of the graphs ...
Linear line
As water flows from a low elevation to a higher elevation through a pipe that changes in diameter
Need more information to determine how the water pressure changes.
Two identical billiard balls traveling at the same speed have a head-on collision and rebound. If the balls had twice the mass, but maintained the same size and speed, how would the rebound be different?
No difference
Hot air is less dense than cold air. Could a hot-air balloon be flown on the Moon, where there is no atmosphere?
No, there is no cold air to displace, so no buoyancy force would exist.
How is the smoke drawn up a chimney affected when a wind is blowing outside?
Smoke rises more rapidly in the chimney.
You are lying in bed and want to shut your bedroom door. You have a bouncy "superball" and a blob of clay, both with the same mass. Which one would be more effective to throw at your door to close it?
Superball
An object that hangs from the ceiling of a stationary elevator by an ideal spring oscillates with a period T. If the elevator accelerates upward with acceleration 2g, what will be the period of oscillation of the object?
T
As you increase the force that you apply while pulling on a rope, which of the following is NOT affected?
The Young's modulus of the rope.
Why does an ocean liner float?
The average density of the ocean liner is less than that of seawater.
A lump of putty and a rubber ball have equal mass. Both are thrown with equal speed against a wall. The putty sticks to the wall. The ball bounces back at nearly the same speed with which it hit the wall. Which object experiences the greater momentum change?
The ball experiences the greater momentum change.
A bowling ball hangs from a 1.0-m-long cord (i) A 200-gram putty ball moving 5.0 m/s hits the bowling ball and sticks to it, causing the bowling ball to swing up; (ii) 200-gram rubber ball moving 5.0 m/s hits the bowling ball and bounces straight back at nearly 5.0 m/s, causing the bowling ball to swing up. Describe what happens.
The ball swings up farther in (ii) than in (i).
A baseball is pitched horizontally toward home plate with a velocity of 110 km/h. In which of the following scenarios does the baseball have the largest change in momentum?
The baseball is hit straight back to the pitcher at a speed of 110 km/h.
Equal masses are suspended from two separate wires. The wires have identical lengths. The first wire has a larger cross-sectional area than the second wire. Which wire will stretch the LEAST?
The first wire will stretch the least.
Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce back from the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greater impact force on your car?
The force would be the same in both cases.
When a guitar is tuned to adjust its pitch, what is it that is changed?
The frequency of the fundamental.
A girl and a boy are riding on a merry-go-round that is turning at a constant rate. The girl is near the outer edge, and the boy is closer to the center. Who has greater linear speed?
The girl has greater linear speed.
A golf ball and an equal-mass bean bag are dropped from the same height and hit the ground. The bean bag stays on the ground while the golf ball rebounds. Which experiences the greater impulse from the ground?
The golf ball
Two spheres have the same radius and equal mass. One sphere is solid, and the other is hollow and made of a denser material. Which one has the bigger moment of inertia about an axis through its center?
The hollow one.
What represents the impulse of the force in a graph of force versus time?
The impulse is equal to the area under the curve.
In a lab environment, you are investigating the impulse of a force exerted on a brick when the brick's speed is reduced from 2.5 m/s to a complete stop. First, you allow the brick to slam into a secured piece of wood, bringing the brick to a sudden stop. Second, you allow the brick to plow into a large slab of gelatin so that the brick comes to a gradual halt. In which situation is there a greater impulse of the force on the brick?
The impulse is the same in both situations.
A pendulum of length L is suspended from the ceiling of an elevator. When the elevator is at rest the period of the pendulum is T. How does the period of the pendulum change when the elevator moves upward with constant acceleration?
The period decreases
A pendulum of length L is suspended from the ceiling of an elevator. When the elevator is at rest the period of the pendulum is T. How does the period of the pendulum change when the elevator moves upward with constant velocity?
The period does not change.
A closed cubical chamber resting on the floor contains oil and a piston. If you push down on the piston hard enough to increase the pressure just below the piston by an amount Δp, which of the following statements is correct?
The pressure everywhere in the oil will increase by Δp.
Tensile strain is
The ratio in the change in length to the original length
A cylindrical rod has equal and opposite forces applied perpendicular to its circular ends. The forces are directed away from the rod, stretching the rod. What type of stress is this rod subject to?
The rod is subject to tensile stress.
Beaker A is filled to the brim with water. Beaker B is the same size and contains a small block of wood which floats when the beaker is filled with water to the brim. Which beaker weighs more?
The same for both
A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the average force during the collision is correct?
The small car and the truck experience the same average force.
A gas-filled balloon is submerged in a fluid. As a result, the balloon is subject to inward forces from all sides. How does the volume of the balloon change?
The volume of the object decreases.
Two wheels having the same radius and mass rotate at the same angular velocity. One wheel is made with spokes so nearly all the mass is at the rim. The other is a solid disk. How do their rotational kinetic energies compare?
The wheel with spokes has about twice the KE.
Three cars, car X, car Y, and car Z, begin accelerating from rest at the same time. Car X is more massive than car Y, which is more massive than car Z. The net accelerating force exerted on each car is identical. After 10 seconds, which car has the most amount of momentum?
They all have the same amount of momentum.
A truck going 15 km/h has a head-on collision with a small car going 30 km/h. Best description
They both have the same change in magnitude of momentum because momentum is conserved.
A small car and a heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push both the car and the truck for the same distance with the same force, what can you say about the momentum and kinetic energy (KE) of the car and the truck? Ignore friction.
They have the same kinetic energy, but the truck has more momentum than the car.
A small car and a heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push both the car and the truck for the same amount of time with the same force, what can you say about the momentum and kinetic energy (KE) of the car and the truck? Ignore friction.
They have the same momentum, but the car has more kinetic energy than the truck.
An astronaut is a short distance away from her space station without a tether rope. She has a large wrench. What should she do with the wrench to move toward the space station?
Throw it directly away from the space station.
Consider a solid uniform sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational?
Translational kinetic energy is larger.
The total mechanical energy of a simple harmonic oscillating system is
a non-zero constant.
For vibrational motion, what term denotes the maximum displacement from the equilibrium position?
amplitude
A small boat coasts at constant speed under a bridge. A heavy sack of sand is dropped from the bridge onto the boat. The speed of the boat
decreases
An object of mass m rests on a frictionless surface and is attached to a horizontal ideal spring with spring constant k. The system oscillates with amplitude A. The oscillation frequency of this system can be increased by
decreasing m.
A wave transports
energy but not matter.
When a baseball curves to the right (a curveball) , air is flowing
faster over the right side than over the left side.
A steel ball sinks in water but floats in a pool of mercury, which is much denser than water. Where is the buoyant force on the ball greater?
floating on the mercury
Water flows in a horizontal pipe that is narrow but then widen and the speed of the water becomes less. The pressure in the water moving in the pipe is
greater where the speed is lower. greater in the wide part.
Bonnie sits on the outer rim of a merry-go-round, and Jill sits midway between the center and the rim. The merry-go-round makes one complete revolution every 2 seconds. Jill's linear velocity is:
half of Bonnie's.
A ballet dancer is spinning in the middle of a horizontal frictionless stage. Which of the following things could he change by moving parts of his body or his whole body?
his angular momentum
The momentum of an isolated system is conserved
in both elastic and inelastic collisions.
An air bubble underwater has the same pressure as that of the surrounding water. As the air bubble rises toward the surface (and its temperature remains constant), the volume of the air bubble
increases.
A railroad car collides with and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system
is half as much as before.
A railroad tank car contains milk and rolls at a constant speed along a level track. The milk begins to leak out the bottom. The car then
maintains a constant speed.
A woman is balancing on a high wire which is tightly strung, as shown in The tension in the wire is
much more than the woman's weight.
The space shuttle, in circular orbit around the Earth, collides with a small asteroid which ends up in the shuttle's storage bay. For this collision,
only momentum is conserved.
Two waves are traveling toward each other along a rope. When they meet, the waves
pass through each other.
For a wave, what term is defined as the time elapsed between two successive crests, or two successive troughs, passing by the same point in space?
period
When you use the approximation sinθ≈θ for a pendulum, you must specify the angle θ in
radians only.
A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will
remain where it is released.
You put two ice cubes in a glass and fill the glass to the rim with water. As the ice melts, the water level
remains the same.
A grandfather clock is "losing" time because its pendulum moves too slowly. Assume that the pendulum is a massive bob at the end of a string. The motion of this pendulum can be sped up by:
shortening the string.
If you used 1000 J of energy to throw a ball, would it travel faster if you threw the ball (ignoring air resistance)
so that it wasn't rotating?
A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They are all uniform and roll without slipping. In what order do they reach the bottom?
sphere, disk, hoop
Suppose you are sitting on a rotating stool holding a 2-kg mass in each outstretched hand. If you suddenly drop the masses, your angular velocity will
stay the same
When you blow some air above a paper strip, the paper rises. This happens because
the air above the paper moves faster and the pressure is lower.
Two equal-magnitude forces are applied to a door at the doorknob. The first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. Which force exerts the greater torque about the door hinge?
the first force (applied perpendicular to the door)
A small solid sphere and a small thin hoop are rolling along a horizontal surface with the same translational speed when they encounter a 20 ∘ rising slope. If these two objects roll up the slope without slipping, which will rise farther up the slope?
the hoop
Suppose you pull a simple pendulum to one side by an angle of 5∘, let go, and measure the period of oscillation that ensues. Then you stop the oscillation, pull the pendulum to an angle of 10∘, and let go. The resulting oscillation will have a period about ________ the period of the first oscillation.
the same as
An object that can float in both water and in oil (whose density is less than that of water) experiences a buoyant force that is
the same when it is floating in water or in oil.
During World War I, Germany used a "Big Bertha" cannon to hurl shells into Paris 30 miles away. This gun also had a very long barrel. What was the reason for using a long barrel in these guns?
to allow the force of the expanding gases from the gunpowder to act for a longer time
Consider a wave on a string moving to the right What is the direction of the velocity of a particle of string at point B?
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