physics 1 exam 4 umsl
A wheel with a 0.10-m radius is rotating at 35 rev/s. It then slows uniformly to 15 rev/s over a 3.0-s interval. What is the angular acceleration of a point on the wheel? 42 rev/s2 0.67 rev/s2 -6.7 rev/s2 -2.0 rev/s2
-6.7 rev/s2
If Earth were twice as massive but it revolved at the same distance from the Sun, its orbital period would be 4 years 1 year two years 6 months
1 YEAR
A fan rotating with an initial angular velocity of 1000 rev/min is switched off. In 2 seconds, the angular velocity decreases to 200 rev/min. Assuming the angular acceleration is constant, how many revolutions does the blade undergo during this time? 100 20 10 125
20
Two uniform solid spheres have the same mass, but one has twice the radius of the other. The ratio of the larger sphere's moment of inertia to that of the smaller sphere is ½ ⅘ 4 2
4
The acceleration due to gravity on the surface of Earth is g. Calling R the radius of Earth, at what distance from Earth's center would the acceleration due to gravity drop to g/16? 16 R R/4 4R 2R
4R
Angles are often measured in radians. How many degrees are there in one radian? 57.3 degrees 1.57 degrees 3.14 degrees 0.0175 degrees
57.3 degrees
Which of the following is required for both rotational and translational equilibrium? Net torque is zero. All of these are required for rotational and translational equilibrium. Net force in the y-direction is zero. Net force in the x-direction is zero.
All of these are required for rotational and translational equilibrium.
An airplane starts from rest at the end of a runway and begins accelerating. The tires of the plane are rotating with an angular velocity that is uniformly increasing with time. On one of the tires, Point A is located on the part of the tire in contact with the runway surface and point B is located halfway between Point A and the axis of rotation. Which one of the following statements is true concerning this situation? Both points have the same instantaneous velocity. Both points have the same centripetal acceleration. Both points have the same tangential acceleration. Each second, point A turns through a greater angle than point B.
Both points have the same instantaneous velocity.
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 smaller angular displacement? The boy has greater angular displacement. Both the girl and the boy have the same nonzero angular displacement. Both the girl and the boy have zero angular displacement. The girl has greater angular displacement.
Both the girl and the boy have the same nonzero angular displacement.
Two small balls, A and B, attract each other gravitationally with a force of magnitude F. If we now double both masses and the separation of the balls, what will now be the magnitude of the attractive force on each one? 16F 8F 4F F
F
A boy and a girl are riding on a merry-go-round that is turning. The boy is twice as far as the girl from the merry-go-round's center. If the boy and girl are of equal mass, which statement is true about the boy's moment of inertia with respect to the axis of rotation? His moment of inertia is twice the girl's. His moment of inertia is 4 times the girl's. The moment of inertia is the same for both. His moment of inertia is (1/4) times the girl's.
His moment of inertia is 4 times the girl's.
The jet engine has angular acceleration of -2.5 rad/s2. Which one of the following statements is correct concerning this situation? The direction of the angular velocity must be clockwise. If the angular velocity is clockwise, then its magnitude must increase as time passes. The direction of the angular acceleration is counterclockwise. The angular velocity must be decreasing as time passes.
If the angular velocity is clockwise, then its magnitude must increase as time passes.
A simple pendulum consists of a ball of mass m suspended from the ceiling using a string of length L. The ball is displaced from its equilibrium position by a small angle θ and released. Which one of the following statements concerning this situation is correct? If the mass were increased, the period of the pendulum would increase. The frequency of the pendulum does not depend on the acceleration due to gravity. If the length of the pendulum were increased, the angular frequency of the pendulum would decrease. The period of the pendulum does not depend on the length of the pendulum.
If the length of the pendulum were increased, the angular frequency of the pendulum would decrease.
An ice skater doing a spin pulls in her arms, decreasing her moment of inertia by a factor of two. How does her angular speed changes? It is reduced by a factor of two. It is reduced by a factor of four. It is increased by a factor of four. It is increased by a factor of two.
It is increased by a factor of two.
A spaceship is traveling to the Moon. At what point is it beyond the pull of Earth's gravity? when it gets above the atmosphere when it is half-way there when it is closer to the Moon than it is to Earth It is never beyond the pull of Earth's gravity.
It is never beyond the pull of Earth's gravity.
A heavy boy and a lightweight girl are balanced on a massless seesaw. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw? The side the boy is sitting on will tilt downward. It is impossible to say without knowing the distances. It is impossible to say without knowing the masses. Nothing, the seesaw will still be balanced.
Nothing, the seesaw will still be balanced.
When is the angular momentum of a system constant? Only when its total kinetic energy is constant. Only when the moment of inertia is constant. Only when the linear momentum and the energy are constant. Only when no net external torque acts on the system. Only when no net external force acts on the system.
Only when no net external torque acts on the system.
Which of the following statements regarding simple harmonic motion is false? The displacement versus time graph for an object in simple harmonic motion is a sine or cosine function. A restoring force acts on an object in simple harmonic motion that is directed in the same direction as the object's displacement. The amplitude of the object in simple harmonic motion is the maximum distance the object moves from its equilibrium position. A restoring force acts on the object that is proportional to the object's displacement from its equilibrium position.
The amplitude of the object in simple harmonic motion is the maximum distance the object moves from its equilibrium position.
Starting from rest, a solid sphere rolls without slipping down an incline plane. At the bottom of the incline, what does the angular velocity of the sphere depend upon? All of these. The angular velocity depends upon the length of the incline. The angular velocity depends upon the height of the incline. The angular velocity depends upon the mass of the sphere.
The angular velocity depends upon the height of the incline.
How do the escape velocities for two rockets, the first weighing 20 N and the second weighing 20,000 N compare? The escape velocity for the lighter rocket is smaller than that for the heavier rocket. The escape velocity for the lighter rocket is the same as that for the heavier rocket. The escape velocity for the lighter rocket is greater than that for the heavier rocket. It is impossible to compare the two escape velocities.
The escape velocity for the lighter rocket is the same as that for the heavier rocket.
An object, which is considered a rigid body, is in equilibrium. Which one of the following statements is false when determining the forces and torques acting on the object? In placing an x-y coordinate system on the object, the +x direction is arbitrary and it can be directed toward any direction that is convenient. A free body diagram of the external forces acting on the object is useful in analyzing this situation. The location of the rotational axis is arbitrary. Therefore, it can be placed at any point on the object that is convenient. The linear acceleration or the angular acceleration of the object may not be equal to zero.
The linear acceleration or the angular acceleration of the object may not be equal to zero.
A block is hung vertically at the end of a spring. When the block is displaced and released, it moves in simple harmonic motion. Which one of the following statements is true concerning the block? The maximum acceleration of the block occurs when its velocity is zero. The velocity of the block is never zero m/s. If the velocity of the block is zero m/s, the acceleration must be zero m/s2. The maximum velocity occurs when the maximum acceleration occurs.
The maximum acceleration of the block occurs when its velocity is zero.
Which of the following statements about the moment of inertia is false? The moment of inertia depends on the angular acceleration of the object as it rotates. Of the particles that make up an object, the particle with the smallest mass may contribute the greatest amount to the moment of inertia. The moment of inertia depends on the location of the rotation axis relative to the particles that make up the object. The moment of inertia depends on the orientation of the rotation axis relative to the particles that make up the object.
The moment of inertia depends on the angular acceleration of the object as it rotates.
Satellite A has twice the mass of satellite B, and moves at the same orbital distance from Earth as satellite B. Compare the speeds of the two satellites. The speed of B is twice the speed of A. The speed of B is one-half the speed of A. The speed of B is one-fourth the speed of A. The speed of B is equal to the speed of A.
The speed of B is equal to the speed of A.
An object is rolling, so its motion involves both rotation and translation. Which of the following statements must be true concerning this situation? The translational kinetic energy may be 0 joules. The total mechanical energy is equal to the sum of the translational and rotational kinetic energies and the gravitational potential energy of the object. The gravitational potential energy must be changing as the object rolls. The rotational kinetic energy must be constant as the object rolls.
The total mechanical energy is equal to the sum of the translational and rotational kinetic energies and the gravitational potential energy of the object.
Consider a solid sphere of radius R and mass M rolling without slipping. Which form of kinetic energy is larger, translational or rotational? Both are equal. Translational kinetic energy is larger. Rotational kinetic energy is larger. You need to know the speed of the sphere to tell.
Translational kinetic energy is larger.
Which one of the following choices is produced when a net torque is applied to a rigid object? a constant angular velocity of the object a constant acceleration of the object a change in the angular velocity of the object a constant angular displacement of the object
a change in the angular velocity of the object
The total mechanical energy of a simple harmonic oscillating system is zero as it passes the equilibrium point. a maximum when it passes the equilibrium point. a non-zero constant. zero when it reaches the maximum displacement.
a non-zero constant.
Which sign convention is correct? there is no sign convention for the direction of rotation caused by a torque a positive torque results in a clockwise rotation a negative torque results in a counterclockwise rotation a positive torque results in a counterclockwise rotation
a positive torque results in a counterclockwise rotation
An astronaut is in a capsule in a stable orbit, about two Earth radii from the center of Earth. Her weight is zero N about one-half of her weight on the surface of Earth. about one-quarter of her weight on the surface of Earth. the same as on the surface of Earth.
about one-quarter of her weight on the surface of Earth.
If the answer to your calculation has units of kg*m2/s, what type of quantity could it be? force work power angular momentum
angular momentum
An object is attached to a vertical spring and bobs up and down between points A and B. Where is the object located when its kinetic energy is a minimum? at either A or B midway between A and B one-fourth of the way between A and B one-third of the way betwen A and B
at either A or B
Because Earth's orbit is slightly elliptical, Earth actually gets closer to the Sun during part of the year. When Earth is closer to the Sun its orbital speed is less than when Earth is farthest away from the Sun. the same as when Earth is farthest away from the Sun. greater than when Earth is farthest away from the Sun. sometimes greater sometimes smaller than when Earth is farthest away from the Sun.
greater than when Earth is farthest away from the Sun.
Because Earth's orbit is slightly elliptical, Earth actually gets closer to the Sun during part of the year. When Earth is closer to the Sun its orbital speed is the same as when Earth is farthest away from the Sun. greater than when Earth is farthest away from the Sun. sometimes greater sometimes smaller than when Earth is farthest away from the Sun. less than when Earth is farthest away from the Sun.
greater than when Earth is farthest away from the Sun.
A person sits on a freely spinning lab stool (no friction). When this person extends her arms, her moment of inertia decreases and her angular velocity decreases. her moment of inertia increases and her angular velocity decreases. her moment of inertia increases and her angular velocity increases. her moment of inertia decreases and her angular velocity increases.
her moment of inertia increases and her angular velocity decreases.
An object in simple harmonic motion is observed to move between a maximum position and a minimum position. The minimum time that elapses between the object being at its maximum position and when it returns to that maximum position is equal to which of the following parameters? frequency period amplitude wavelength
period
Two objects attract each other gravitationally. If the distance between their centers is cut in half, the gravitational force is cut to one fourth. is cut in half. doubles. quadruples.
quadruples
A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They all roll without slipping. In what order do they reach the bottom? sphere, disk, hoop hoop, disk, sphere hoop, sphere, disk disk, hoop, sphere
sphere, disk, hoop
Rolling without slipping depends on tension between the rolling object and the ground. normal force between the rolling object and the ground. kinetic friction between the rolling object and the ground. static friction between the rolling object and the ground.
static friction between the rolling object and the ground.
The highest tides occur when the Sun and the Moon are on the same side of Earth. the Sun and the Moon are on opposite sides of Earth. the Sun, Moon, and Earth form a right-angled triangle with Earth at the 90° vertex. the Sun, Moon, and Earth form a right-angled triangle with the Sun at the 90° vertex.
the Sun and the Moon are on the same side of Earth.
In the equation for torque, τ=rFsinϕ, what is r? the side of the triangle that is opposite the angle the perpendicular distance from the point of rotation to the point where the force acts the radius of the object the distance from the point of rotation to the point where the force acts
the distance from the point of rotation to the point where the force acts
Complete the following sentence: In harmonic motion, resonance occurs when the driving frequency is the same as the natural frequency of the system. the energy in the system is a minimum. the system is critically damped. the system is overdamped.
the driving frequency is the same as the natural frequency of the system.
Two equal forces are applied to a door at the doorknob. The first force is applied perpendicular to the door; the second force is applied at 30° to the plane of the door. Which force exerts the greater torque? the first applied perpendicular to the door both exert zero torques the second applied at an angle both exert equal non-zero torques
the first applied perpendicular to the door
A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry-go-round. As he does this, it is true to say that the moment of inertia of the system decreases and the angular speed increases. the moment of inertia of the system decreases and the angular speed decreases. the moment of inertia of the system decreases and the angular speed remains the same. the moment of inertia of the system increases and the angular speed increases. the moment of inertia of the system increases and the angular speed decreases.
the moment of inertia of the system decreases and the angular speed increases.
Angular momentum cannot be conserved if the angular acceleration changes. the angular velocity changes. the moment of inertia changes. the net torque is not zero.
the net torque is not zero.
Complete the following statement: For a wheel that turns with constant angular speed, the angular displacement of a point on the rim is constant. each point on the rim moves at constant velocity. the wheel turns through "equal angles in equal times." each point on its rim moves with constant acceleration.
the wheel turns through "equal angles in equal times."
When you ride a bicycle forward, in what direction is the angular velocity of the wheels? forwards to your right to your left backwards
to your left
Under which one of the following conditions does the motion of a simple pendulum approximate simple harmonic motion? when the pendulum swings rapidly. when the length of the pendulum is more than twice the diameter of the bob. when the pendulum swings through a small angle. when the pendulum swings slowly.
when the pendulum swings through a small angle.
