Physics 1408 Schaub Conceptual Questions

Water flows through a pipe. The diameter of the pipe at point B is larger than at point A. Where is the water pressure greatest?

at point B

When you apply the torque equation to an object in equilibrium, the axis about which torques are calculated

can be located anywhere.

A block of mass m sits at rest on a rough inclined ramp that makes an angle(theta) with the horizontal. What must be true about force of static friction f on the block?

f=mg*sin(theta)

An object of mass M oscillates on the end of a spring. To triple the period, replace the object with one of mass

9M (T=2pi sqrt(M/K))

A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?

12P (P=W*T => P=6W * T/2)

Two horizontal pipes are the same length, but pipe B has twice the diameter of pipe A. Water undergoes laminar flow in both pipes, subject to the same pressure difference across the lengths of the pipes. If the flow rate in pipe A is Q, what is the flow rate in pipe B?

16Q

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 (P=m*v ; 2m*2v => 4mv => 4P)

An object at rest begins to rotate with a constant angular acceleration. If this object rotates through an angle(theta) in time t, through what angle did it rotate in the time 2t?

4(theta) (theta= wt + (1/2)at^2

For which value of (theta) is the range of a projectile fired from ground level a maximum?

45 degrees above the horizontal. (plug in each value into the projectile function: 45 is = to 1)

You decrease your distance from a sound source that is radiating equally in all directions to 1/3 the original distance. What happens to the intensity of the sound? It reduces to

9 times its original value

Which of the following situations is impossible?

An object has constant non-zero velocity and changing acceleration.

Consider a uniform hoop of radius R (I=MR^2) and mass M rolling without slipping. Which is larger, its translational kinetic energy or its rotational kinetic energy?

Both are equal

A car drives at steady speed around a perfectly circular track.

Both the acceleration and net force on the car point inward.

A satellite is in orbit around the earth. Which one feels the greater force?

Earth and the satellite feel exactly the same force.

Two small objects, with masses m and M, are originally a distance r apart, and the magnitude of the gravitational force on each one is F. The masses are changed to 2m and 2M, and the distance is changed to 4r. What is the magnitude of the new gravitational force?

F/4 (F=mM/r^2)=> F= 4mM/16=mM/r^2 => F/4

Two pure tones are sounded together and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

It could either increase or decrease.

A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the velocity of the rock right before it hits the ground?

It is equal to the magnitude of its initial velocity.

The water pressure to an apartment is increased by the water company. The water enters the apartment through an entrance valve at the front of the apartment. Where will the increase in the static water pressure be greatest when no water is flowing in the system?

It will be the same at all the faucets.

Suppose that a car traveling to the west (-x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?

Its acceleration is positive. (velocity is negative; if the car would have been going in the y direction it would be opposite, such as acceleration is negative and velocity is positive)

If the initial speed of a projectile is doubled

Its range will quadruple.

A projectile is fired from ground level on a horizontal plane. If the initial speed of the projectile is now doubled, and we neglect air resistance.

Its range will quadruple. (R=(V^2(initial velocity) * sin2theta)/g)

A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Which of the following statements about the direction of the velocity and acceleration of the ball as it is going up is correct?

Its velocity points upward and its acceleration points downward.

When is the angular momentum of a system constant?

Only when no net external torque acts on the system.

A box is being moved with a velocity v by a force P (in the same direction as v) along a level horizontal floor. The normal force is N, the kinetic frictional force if f_k, and the weight is mg. Which one of the following statements is correct?

P does positive work, N and mg do zero work, and f_k does negative work.

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically. Which object is traveling faster when it hits the level ground below if neither of them experiences any air resistance?

The ball

Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat?

The buoyant force is the same in both cases.

Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by the object.

The displacement is either less than or equal to the distance traveled.

Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude?

The first force (at the midpoint).

Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance? (there could be more than one correct choice)

The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.

An object is moving with constant non-zero velocity. Which of the following statements about it must be true?

The net force on the object is zero.

Two vibrating systems with the same resonant frequency are compared. System A has a bandwidth one-half the bandwidth of system B. Which of the following statements is true concerning the two systems?

The quality factor of system A is two times the quality factor of system B.

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 equal to the speed of A.

Simple harmonic motion is defined by which of the following conditions?

The vibrations are the result of a linear restoring force & The vibrations occur about an equilibrium position.

When a rigid object rotates about a fixed axis, what is true about all the points in the object?

They all have the same angular speed.

Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street? Neglect air resistance.

They are traveling at the same speed.

If an object remains at rest, then both the net torque and the net force on the object MUST be zero.

True

Two steel wires have the same length and are under the same tension. But wire A has twice the diameter of wire B. Which of the following is true?

Wire B stretches four times as much as wire A.

A person sits on a freely spinning lab stool that has no friction in its axle. When this person extends her arms,

her moment of inertia increases and her angular speed decreases

You are driving at 75 km/h. Your sister follows in a car behind at 90 kn/h. When you honk your horn, your sister hears a frequency

higher than the frequency you hear

The momentum of an isolated system is conserved

in both elastic and inelastic collisions.

If both the mass of a simple pendulum and its length are doubled, the period will

increase by a factor of sqrt2 (T = 2pi sqrt(l/g))

When a ball is thrown straight up with no air resistance, the acceleration at its highest point

is downward

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.

Which of the following would NOT be one of the four fundamental forces of nature?

strong electron force & weak electromagnetic force

Newton's second law of motion predicts that

the acceleration of an object is directly proportional to the net force on the object and indirectly proportional to the object's mass

A string of mass m is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the mass of the string is increased to 4 m but with no change in the length or tension?

v/2