Exam 1: Conservation Laws Constrain Interactions

Suppose a jet is cruising at a constant velocity due east. At the instant the jet is above your head, what is the direction of the jet's angular momentum around you? Choose from the possible directions presented in problem C7T.3, remembering that this is a top view, with A corresponding to north, C to east, and so on.

If two moving objects collide, we can always orient our reference frame so that the collision takes place entirely in the $x y$ plane.

In the hypothetical atomic interaction shown in figure C9.13, assume that initially the atoms have zero velocity at a separation of $r=0.2 \mathrm{~nm}$ . How will their separation subsequently evolve with time?

In a situation where an object can move only along the $x$ axis, a book states "the force on the object is $\mathrm{F}=$ $k x$ , where $k$ is a constant, and $x$ is the object's position coordinate." Is $F$ being used here as a shorthand symbol for $|\vec{F}|(A)$ or $F_{x}(C)$ ? $\bullet$ A $\bullet$ C

Consider the types of reference frames listed below. (NRF = nonrotating frame) -A NRF attached to a satellite orbiting the earth 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 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. -The earth's atmosphere

Suppose a moving cart (cart $A$ ) hits an identical cart (cart $B$ ) at rest. Cart $B$ remains at rest after the collision, and cart $A$ rebounds with a speed equal to its original speed. Cart $B$ must have participated in some other interaction during the collision process,

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 heat energy released by a 1-kg bottle of water as its temperature decreases by $1^{\circ} \mathrm{C}$ could (if we could convert it to gravitational potential energy) lift that bottle hundreds of meters into the air.

The thermal energy of a block of ice at $0^{\circ} \mathrm{C}$ melting to a puddle of water at $0^{\circ} \mathrm{C}$ in a cup at room temperature

In the situation discussed in problem C4T.10, which would be the easiest reasonably valid frame to use?

A railroad car collides with a similar car at rest. The cars lock together. Such a process must convert a significant fraction of the originally moving car's kinetic energy to thermal energy

The speed $V$ of sound waves in a gas like air might plausibly depend on the gas's pressure $P$ (which has units of $\mathrm{N} / \mathrm{m}^{2}$ ), the gas's density $\rho$ (which has units of $\mathrm{kg} / \mathrm{m}^{3}$ ) and its temperature $T$ (which has units of $\mathrm{K}$ ), and some unitless constant $C$ . Assuming that no other quantities are relevant, which of the following formulas might possibly correctly give the speed of sound in a gas?

Suppose sand is leaking from an unpowered but moving railroad car. Since the sand is moving forward along with the car as it leaks out, it carries kinetic energy out of the car. This mass transfer will

Suppose I throw a ball toward the floor. It hits the floor and rebounds upward. What type of interaction causes the ball to rebound?

Which of the following expressions gives the correct units for the volt in terms of base SI units?

In the situation described in problem C10T.5, will the car's internal energy increase, decrease, or remain unchanged? (Be prepared to explain your answer in terms of the momentum requirement and the work done.)

A hydrogen atom consists of an electron (with negative charge) orbiting a proton (with positive charge). With the conventional definition of the reference position for electrostatic potential energy, the electrostatic potential energy for this system

Suppose a $1.0-\mathrm{kg}$ object traveling rightward at $1.0 \mathrm{~m} / \mathrm{s}$ hits a $3.0 \mathrm{~kg}$ object at rest. Afterward, we observe the lighter object to move leftward with a speed of $0.75 \mathrm{~m} / \mathrm{s}$ . What impulse did the collision interaction give the smaller object at the expense of the larger?

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