Exam 1: Conservation Laws Constrain Interactions

$|\vec{u}-\vec{w}| \geq|\vec{u}|-\mid \vec{w} \|$ for all vectors $\vec{u}$ and $\vec{w}$

According to the Stefan-Boltzmann law, an object at room temperature that is sitting in a room (also at room temperature) must emit electromagnetic radiation. Since it is losing energy by emitting this radiation, why does its temperature remain constant?

Consider the solar system as a "system" of particles. Which of the below qualify as internal interactions (A) and which as external interactions (E)? -The gravitational interaction between a given planet and the sun

If global warming proceeds during the next century as anticipated, the polar ice caps may melt, substantially raising sea levels around the world (and flooding coastal cities such as New York and New Orleans). What effect will this have on the duration of the day?

A car moves backward $10 \mathrm{~m}$ in $2 \mathrm{~s}$ at a steady rate. The car's speed is therefore $-5 \mathrm{~m} / \mathrm{s}$

When an object slides down a frictionless incline, The interaction does not change the object's kinetic energy

Suppose we put a ball at rest on a rug and then start pulling the rug out from under the ball in a certain direction. The ball rolls without slipping on the rug as the rug moves under it. The friction force that the contact interaction between the rug and ball exerts on the ball does

We can describe a vector's magnitude and direction without a reference frame

The two stars in a binary star system revolve around each other with a certain period $T$ . Which of the quantities listed below is not likely to be a part of the formula for this revolution period?

The emergency blankets in some first-aid kits consist of very thin Mylar that has been coated with aluminum to make it shiny. How can such thin plastic be a blanket? -Which mechanism does it least effectively suppress?

Consider the solar system as a "system" of particles. Which of the below qualify as internal interactions (A) and which as external interactions (E)? -The magnetic interaction between the sun and the earth (both have magnetic fields)

Which of the following frames would be an appropriate inertial reference frame for analyzing the effects on the earth of its gravitational interaction with the moon? -A frame attached to the entire solar system's CM A) if the frame is appropriate B) if it would be bad for this purpose.

Which of the following frames would be an appropriate inertial reference frame for analyzing the effects on the earth of its gravitational interaction with the moon? -A frame attached to the earth's surface A) if the frame is appropriate B) if it would be bad for this purpose.

Consider the solar system as a "system" of particles. Which of the below qualify as internal interactions (A) and which as external interactions (E)? - The gravitational interaction between the earth and the International Space Station

Which of the following things is an "extended object"? For each item, answer "A" if the item is an acceptable extended object, " $\mathrm{B}$ " if the definition of an extended object applies badly to the item, and " $\mathrm{D}$ " if it is debatable. -Sugar molecules dissolved in a cup of water

Consider the solar system as a "system" of particles. Which of the below qualify as internal interactions (A) and which as external interactions (E)? -The gravitational interaction between the sun and the larger galaxy

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.

Consider the types of reference frames listed below. (NRF = nonrotating frame) -A reference frame attached to a roller-coaster car A. A NRF in deep space B. A NRF that is freely floating C. A NRF attached to the earth's center of mass D. A frame attached to the earth's surface (or a similarly slowly rotating object) E. A frame moving at a constant velocity relative to one of the frame types described above F. A noninertial frame

Which of the following frames would be an appropriate inertial reference frame for analyzing the effects on the earth of its gravitational interaction with the moon? -A frame attached to the sun's CM A) if the frame is appropriate B) if it would be bad for this purpose.

A person is sitting at rest on a stool that is free to rotate about a vertical axis. The person holds in one hand a bicycle wheel that spins rapidly counterclockwise (when viewed from above). The person then stops the wheel with the other hand. What happens as a result?