Chapter S4 Activites

Which of the forces are unimportant on large scales because they can be felt only across distances about the size of atomic nuclei or smaller?

-weak force -strong force

Match the terms in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each term only once.

1. The exclusion principle is consistent with the notion that two electrons cannot exist in the same place at the same time. 2. Hydrogen nuclei in the core of the Sun do not seem to be moving quite fast enough to overcome the electromagnetic force of repulsion, but they nevertheless can fuse together thanks to the process we call quantum tunneling. 3. The location, momentum, and spin of a proton are part of what we call the proton's quantum state. 4. Brown dwarfs do not collapse due to electron degeneracy pressure. 5. A balloon filled with air does not collapse due to thermal pressure. 6. Knowing both the exact position and velocity of an electron simultaneously is a violation of the uncertainty principle. 7. Neutron stars do not collapse into black holes because they are supported against the crush of gravity by neutron degeneracy pressure.

The electromagnetic force is much stronger than gravity over short distance scales. So why doesn't it dominate over gravity for large masses, such as planets, stars, and galaxies?

Because large masses are electrically neutral.

Listed below are characteristics and effects of the four fundamental forces: gravity, electromagnetism, the strong force, and the weak force. Match each item to the correct fundamental force.

GRAVITY: -governs large-scale structure of the universe -weakest force (across short distances) ELECTROMAG: -transmitted by photons -affects only electrically charged particles STRONG: -transmitted by gluons -holds nuclei together WEAK: -governs nuclear fission and radioactive decay

How does the existence of helium nuclei (with 2 protons and 2 neutrons) demonstrate that there must be a force in nature that is stronger than the electromagnetic force?

The electromagnetic force makes protons repel, so there must be a stronger force that keeps them together.

Which part of the figure shows an example of energy conservation?

both Figures a and b

Following are the four fundamental forces. Rank these forces from left to right based on their relative strengths between two protons located within the nucleus of an atom, from weakest to strongest.

gravity, weak, electromagnetic, strong

Suppose that, rather than starting with an electron and a positron, the event shown in Figure a started with two electrons. What would happen?

move away from each other without meeting.

Which part of the figure shows an example of matter/antimatter annihilation?

only Figure a

Following are the four fundamental forces. Rank these forces from left to right based on their relative strengths acting between Earth and the Sun, from weakest to strongest. If you think two (or more) forces have equal strength (or essentially zero strength) in this case, show the equality by dragging one on top of the other(s)

weak/strong (together), electromag, gravity

Following are the four fundamental forces. Rank these forces from left to right based on their relative strengths between two protons separated by a few centimeters, from weakest to strongest. If you think two (or more) forces have equal strength (or essentially zero strength) in this case, show the equality by dragging one on top of the other(s).

weak/strong (together), gravity, electromagnetic