Exam 1: Conservation Laws Constrain Interactions

A soccer ball hits a wall. In the process, the place where the ball meets the wall is pushed about $5 \mathrm{~cm}$ toward the ball's center. Is the work done on the ball by the contact interaction between it and the wall positive, negative, or zero?

A 100-g sample of a certain substance undergoes a transformation of some kind that releases 20,000 $\mathrm{J}$ of energy. What kind of transformation is this likely to be?

If you rub your hands together, they get warmer (try it!). Rubbing therefore heats your hands

Suppose we use a string to suspend a ball from a hook in the ceiling. As the ball swings back and forth, which interaction does work on the system if -we consider the system to be the ball or

What type of interaction is involved? A. A tension interaction B. An electrostatic interaction C. A friction interaction D. A compression interaction E. Other (specify)

Two wheels have the same total mass $M$ and radius $R$ . One wheel is a uniform disk. The other is like a bicycle wheel, with lightweight spokes connecting the rim to a small hub. Which likely has the larger moment of inertia?

Substance $A$ has twice the specific "heat" as substance $B$ . Suppose we have a $50-g$ block of each substance at a common initial temperature of $100^{\circ} \mathrm{C}$ . We then put both blocks into a well-insulated cup containing $500 \mathrm{~g}$ of water at $20^{\circ} \mathrm{C}$ , and wait until the objects' and the water's temperatures no longer change. - Which block has given up more energy to the water?

An object of mass $m$ traveling at speed $\vec{v}_{0}$ in the $+x$ direction hits an identical object at rest. Characterize each of the collision outcomes shown below as being (A) absurd or (C) credible. (The collisions are not necessarily elastic, but they are not super-elastic.) -

According to the definition of "science" given in this chapter, astrology is not a science. What does it lack?

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

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

An empty floating boat interacts gravitationally with the earth. A different interaction with something else keeps the boat from responding to the gravitational interaction by sinking. -What type of interaction is involved?

Which of the following statements involve notation, unit, or conceptual errors? For each statement, answer $A$ if the statement is acceptable, or $E$ if it is erroneous. -If an object moves at a rate of $5 \mathrm{~m} / \mathrm{s}$ in the $-x$ direction, then $\vec{v}_{x}=-5 \mathrm{~m} / \mathrm{s}$ .

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 vacuum between galaxies

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-moon system's CM A) if the frame is appropriate B) if it would be bad for this purpose.

Suppose we put a $0.3-\mathrm{kg}$ hunk of ice at $0^{\circ} \mathrm{C}$ into an insulating thermos bottle filled with $1000 \mathrm{~g}$ of water at $20^{\circ} \mathrm{C}$ . What will be the system's final temperature?

Suppose that $\vec{u}$ and $\vec{w}$ both have nonzero $y$ and $z$ components, but both also have zero $x$ components. Which components of $\vec{q}=\vec{u} \times \vec{w}$ are nonzero? Select or indicate all the letters that apply.

An object of mass $m$ traveling at speed $\vec{v}_{0}$ in the $+x$ direction hits an identical object at rest. Characterize each of the collision outcomes shown below as being (A) absurd or (C) credible. (The collisions are not necessarily elastic, but they are not super-elastic.) -

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

Suppose the interaction between two atoms has the effective potential energy curve shown below: I have marked the vertical scale on this graph using an arbitrary energy unit we'll call bondits. -Suppose instead we know that at $t=0$ the atoms are at rest at a separation of $0.4 \mathrm{~nm}$ . What minimum energy is required to break the bond in this case?