Question 1

To which of the following two-object systems can we apply conservation of momentum, and why? In each case, answer "A" if we can apply conservation of momentum because the system floats in space, "F" if it's because the system is functionally isolated, " $C$ " if it's because the system undergoes a collision, and " $\mathrm{D}$ " if momentum is not conserved at all because the system is not isolated.
-An isolated star passes through a well-defined cloud of gas, and is slowed by friction in this process. (Assume that we can keep track of the cloud's momentum.)

Accepted Answer

The answer of To which of the following two-object systems...

Question 2

To which of the following two-object systems can we apply conservation of momentum, and why? In each case, answer "A" if we can apply conservation of momentum because the system floats in space, "F" if it's because the system is functionally isolated, " $C$ " if it's because the system undergoes a collision, and " $\mathrm{D}$ " if momentum is not conserved at all because the system is not isolated.
-Two people dance the tango.

Accepted Answer

The answer of To which of the following two-object systems...

Question 3

To which of the following two-object systems can we apply conservation of momentum, and why? In each case, answer "A" if we can apply conservation of momentum because the system floats in space, "F" if it's because the system is functionally isolated, " $C$ " if it's because the system undergoes a collision, and " $\mathrm{D}$ " if momentum is not conserved at all because the system is not isolated.
-Two people riding personal hovercraft tug on each other with a rope.

Accepted Answer

The answer of To which of the following two-object systems...

Question 4

To which of the following two-object systems can we apply conservation of momentum, and why? In each case, answer "A" if we can apply conservation of momentum because the system floats in space, "F" if it's because the system is functionally isolated, " $C$ " if it's because the system undergoes a collision, and " $\mathrm{D}$ " if momentum is not conserved at all because the system is not isolated.
-A cannonball drops to the earth and lands with a thud, burying itself in the ground.

Accepted Answer

The answer of To which of the following two-object systems...

Question 5

When is friction a potential problem for applying conservation of momentum to a system?

Accepted Answer

Friction as an external interaction can introduce an external force to the system, violating the condition for the conservation of momentum which requires that no external forces act on the system. Conservation of momentum applies only when the net external force on a system is zero.

Question 6

A basketball bounces off the floor. It is difficult to apply conservation of momentum usefully to the ballearth system in this case because

Accepted Answer

The answer of A basketball bounces off the floor. It...

Question 7

The following diagrams show hypothetical results for collisions between identical balls floating in space. One ball was originally moving to the right along the dashed line before striking the other ball at rest. (The collision was not necessarily head-on.) The arrows depict the balls' final velocities. Which outcomes are physically believable? 
-
A) if it is absurd.
B)if the outcome is believable

Accepted Answer

The answer of The following diagrams show hypothetical results for...

Question 8

The following diagrams show hypothetical results for collisions between identical balls floating in space. One ball was originally moving to the right along the dashed line before striking the other ball at rest. (The collision was not necessarily head-on.) The arrows depict the balls' final velocities. Which outcomes are physically believable? 
-
A) if it is absurd.
B)if the outcome is believable

Accepted Answer

The answer of The following diagrams show hypothetical results for...

Question 9

The following diagrams show hypothetical results for collisions between identical balls floating in space. One ball was originally moving to the right along the dashed line before striking the other ball at rest. (The collision was not necessarily head-on.) The arrows depict the balls' final velocities. Which outcomes are physically believable? 
-
A) if it is absurd.
B)if the outcome is believable

Accepted Answer

The answer of The following diagrams show hypothetical results for...

Question 10

The following diagrams show hypothetical results for collisions between identical balls floating in space. One ball was originally moving to the right along the dashed line before striking the other ball at rest. (The collision was not necessarily head-on.) The arrows depict the balls' final velocities. Which outcomes are physically believable? 
-
A) if it is absurd.
B)if the outcome is believable

Accepted Answer

The answer of The following diagrams show hypothetical results for...

Question 11

The following diagram shows a collision between identical balls floating in space. The balls have initial velocities $\overrightarrow{v_{1}}$ and $\overrightarrow{v_{2}}$. After the collision, one of the balls has velocity $\overrightarrow{v_{3}}$. Which of the displayed arrows most closely corresponds to the final velocity of the other ball?

Accepted Answer

The answer of The following diagram shows a collision between...

Question 12

If a change in nozzle design increases a given rocket engine's exhaust speed by a factor of two, by what factor does this increase or decrease the amount of propellant needed to get its payload to a specific final velocity? (Assume the payload and engine mass is small compared to that of the fuel, and choose the closest answer.)

Accepted Answer

The answer of If a change in nozzle design increases...

Question 13

Initially, the light puck is moving east at $3 \mathrm{~m} / \mathrm{s}$ while the heavy puck is moving west at $2 \mathrm{~m} / \mathrm{s}$. The final velocity of the conjoined pucks is

Accepted Answer

The answer of Initially, the light puck is moving east...

Question 14

Initially, the light puck is moving west at $4 \mathrm{~m} / \mathrm{s}$ while the heavy puck is moving south at $2 \mathrm{~m} / \mathrm{s}$. The final velocity of the conjoined pucks is

Accepted Answer

The final velocity direction is southwest because the light puck contributes a westward component and the heavy puck contributes a southward component to the motion. When combined, these components result in a southwest direction due to vector addition.

Question 15

Initially, the light puck was moving south and the final speed of the conjoined pucks is zero. The original velocity of the heavy puck must have been northward

Accepted Answer

For the final speed of the conjoined pucks to be zero, the heavy puck must have been moving in the opposite direction (northward) to the light puck's southward motion, with enough momentum to stop both pucks, adhering to the conservation of momentum principle.

Question 16

A cylinder rolls, without slipping, down an incline directly toward you. The cylinder's angular velocity $\vec{\omega}$ points in which direction?

Accepted Answer

The right-hand rule for angular velocity dictates that if you curl the fingers of your right hand in the direction of the cylinder's rotation (which is clockwise when viewed from above as it rolls toward you), your thumb points to the right, indicating the direction of the angular velocity vector.

Question 17

A cylinder rolls, without slipping, down an incline directly toward you. The contact interaction between the cylinder and the incline exerts a frictional torque on the cylinder. What is this torque's direction?

Accepted Answer

The answer of A cylinder rolls, without slipping, down an...

Question 18

Consider a rectangular book. The book is (approximately) symmetric (in the sense defined in the chapter) for rotations around an axis that is perpendicular to its face and goes through its center of mass

Accepted Answer

A rectangular book is symmetric for rotations around an axis that is perpendicular to its face and goes through its center of mass because rotating it 180 degrees around this axis will result in the book appearing the same due to its rectangular shape and uniform distribution of mass.

Question 19

Consider a point $P$ midway between two particles, one with charge $-q$ and one with charge $q$. The potential $\phi$ at point $P$ is zero.

Accepted Answer

The answer of Consider a point $P$ midway between two...

Question 20

The letter $\mathrm{N}$ is symmetric (in the sense defined in this chapter) for rotations around an axis going through its center that points in which of the following directions?

Accepted Answer

The letter "N" is symmetric for rotations around an axis perpendicular to its plane, as it looks the same when rotated 180 degrees around this axis.

Quiz 1: Conservation Laws Constrain Interactions

When is friction a potential problem for applying conservation of momentum to a system?

A basketball bounces off the floor. It is difficult to apply conservation of momentum usefully to the ballearth system in this case because

Initially, the light puck is moving east at $3 \mathrm{~m} / \mathrm{s}$ while the heavy puck is moving west at $2 \mathrm{~m} / \mathrm{s}$ . The final velocity of the conjoined pucks is

Initially, the light puck is moving west at $4 \mathrm{~m} / \mathrm{s}$ while the heavy puck is moving south at $2 \mathrm{~m} / \mathrm{s}$ . The final velocity of the conjoined pucks is

Initially, the light puck was moving south and the final speed of the conjoined pucks is zero. The original velocity of the heavy puck must have been northward

A cylinder rolls, without slipping, down an incline directly toward you. The cylinder's angular velocity $\vec{\omega}$ points in which direction?

A cylinder rolls, without slipping, down an incline directly toward you. The contact interaction between the cylinder and the incline exerts a frictional torque on the cylinder. What is this torque's direction?

Consider a rectangular book. The book is (approximately) symmetric (in the sense defined in the chapter) for rotations around an axis that is perpendicular to its face and goes through its center of mass

Consider a point $P$ midway between two particles, one with charge $-q$ and one with charge $q$ . The potential $\phi$ at point $P$ is zero.

The letter $\mathrm{N}$ is symmetric (in the sense defined in this chapter) for rotations around an axis going through its center that points in which of the following directions?

Quiz 1: Conservation Laws Constrain Interactions

When is friction a potential problem for applying conservation of momentum to a system?

A basketball bounces off the floor. It is difficult to apply conservation of momentum usefully to the ballearth system in this case because

Initially, the light puck is moving east at 3 m/s3 \mathrm{~m} / \mathrm{s}3 m/s while the heavy puck is moving west at 2 m/s2 \mathrm{~m} / \mathrm{s}2 m/s . The final velocity of the conjoined pucks is

Initially, the light puck is moving west at 4 m/s4 \mathrm{~m} / \mathrm{s}4 m/s while the heavy puck is moving south at 2 m/s2 \mathrm{~m} / \mathrm{s}2 m/s . The final velocity of the conjoined pucks is

Initially, the light puck was moving south and the final speed of the conjoined pucks is zero. The original velocity of the heavy puck must have been northward

A cylinder rolls, without slipping, down an incline directly toward you. The cylinder's angular velocity ω⃗\vec{\omega}ω points in which direction?

A cylinder rolls, without slipping, down an incline directly toward you. The contact interaction between the cylinder and the incline exerts a frictional torque on the cylinder. What is this torque's direction?

Consider a rectangular book. The book is (approximately) symmetric (in the sense defined in the chapter) for rotations around an axis that is perpendicular to its face and goes through its center of mass

Consider a point PPP midway between two particles, one with charge −q-q−q and one with charge qqq . The potential ϕ\phiϕ at point PPP is zero.

The letter N\mathrm{N}N is symmetric (in the sense defined in this chapter) for rotations around an axis going through its center that points in which of the following directions?

Initially, the light puck is moving east at $3 \mathrm{~m} / \mathrm{s}$ while the heavy puck is moving west at $2 \mathrm{~m} / \mathrm{s}$ . The final velocity of the conjoined pucks is

Initially, the light puck is moving west at $4 \mathrm{~m} / \mathrm{s}$ while the heavy puck is moving south at $2 \mathrm{~m} / \mathrm{s}$ . The final velocity of the conjoined pucks is

A cylinder rolls, without slipping, down an incline directly toward you. The cylinder's angular velocity $\vec{\omega}$ points in which direction?

Consider a point $P$ midway between two particles, one with charge $-q$ and one with charge $q$ . The potential $\phi$ at point $P$ is zero.

The letter $\mathrm{N}$ is symmetric (in the sense defined in this chapter) for rotations around an axis going through its center that points in which of the following directions?