Exam 1: Conservation Laws Constrain Interactions

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 contact interactions between the earth and a car moving on the earth's surface

A bicyclist rounding a curve at a constant speed is receiving a nonzero net flow of momentum.

In the hypothetical atomic interaction shown in figure C9.13, the force between the atoms is attractive within what ranges of the interatomic separation $r$ ?

Four people are sitting at the lettered positions on the rim of a merry-go-round shown below that is slowly turning clockwise. You throw a fairly massive ball horizontally to one of these people, who catches it. To which person should you throw the ball so that catching it most effectively increases the merry-go-round's rotation rate?

Two hockey pucks are initially at rest on a horizontal plane of frictionless ice. Puck $A$ has twice the mass of puck $B$ . Suppose we apply the same constant force on each puck until each puck has crossed a finish line $1 \mathrm{~m}$ away from its starting point. How do the puck's kinetic energies compare when each crosses the finish line?

A heavy ball swings at the end of a chain connected to a hook in the ceiling. Suppose I pull the ball away from its equilibrium position, hold it against my nose (with the chain taut), and then release the ball from rest. The ball swings away and then back toward my face. As long as I don't move, and the ball is left alone, I can be confident that the ball will not smash my nose

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?

The angular momentum of a particle can be nonzero even if it moves in a straight line

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.)

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

Which has the larger kinetic energy, a 50-kg person running at a speed of $2 \mathrm{~m} / \mathrm{s}$ , or a $5-\mathrm{g}$ nickel falling at a speed of $200 \mathrm{~m} / \mathrm{s}$ ?

Consider the displacement vectors shown below. - Which vector (if any) is equal to $\vec{A}$

Suppose you have a small cart at rest. You have two different objects that you might throw at the cart to get it moving: a 57-g tennis ball and a 57-g lump of sticky clay. Other things being equal, which should you throw at the cart to maximize the cart's final speed?

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

Various objects are released from rest at the same time and vertical position and roll without slipping along an incline. -Which will reach the bottom first?

Consider the displacement vectors shown below. -Which is equal to $2 \vec{B}$ ?

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

An object of mass $m$ moving in a $+x$ direction collides head-on with an object at rest with mass $3 m$ . After this elastic collision, the first object

Which of the following statements best describes the relationship between the energy $E_{A}$ required to increase a 1000-kg car's speed from 0 to $23 \mathrm{~m} / \mathrm{s}$ (about $50 \mathrm{mi} / \mathrm{h}$ ) and the energy $E_{B}$ required to increase the temperature of $1 \mathrm{gal}\left(\approx 3.8 \mathrm{~kg}\right.$ ) of lemonade from refrigerator temperature (about $5^{\circ} \mathrm{C}$ ) to room temperature?

We can consider a set of all chlorine atoms in a block of salt (sodium chloride) to be a "system."