An Introduction to Physics Trivia Quiz

Answer: Gravity accelerates all masses equally

When objects fall in a vacuum, the only force acting on them is gravity, because air resistance is nil. The force of gravity produces the same acceleration regardless of an object's mass. The whole idea goes back to Galileo, who understood that the difference we see on our boring old planet comes from the atmosphere playing games with air resistance, not because gravity is behaving differently.

Gravity does pull harder on heavier objects with a greater force (weight is what measures that force after all), but there's a catch. More massive objects also have proportionally more inertia. The two effects cancel each other out perfectly and, voilą, you've got the same acceleration. Physics does enjoy this kind of nifty balance... except when it doesn't.

This principle was demonstrated beautifully on the Moon during the Apollo 15 mission, when David Scott dropped a hammer and a feather at the same time. Both hit the lunar surface together, proving that gravity doesn't fat-shame when air is not around to meddle. The feather did not float or flutter. It just fell, like everything else.

Answer: Refraction

When light moves from one medium to another, such as from air into water or glass, its speed changes. The change in speed makes light change direction, a phenomenon we lovingly call refraction. The bending happens right at the boundary between the two materials, making straight objects look bent when partially submerged. Consider a straw in a glass of water. The straw appears to bend where the two mediums change. To paraphrase Steven Wright, this is why men don't take baths.

If you want to get all technical, refraction depends on the refractive index of a material, which is a measure of how much that material slows light down. Glass and water both have higher refractive indices than air, so light entering them is forced to adjust its path. Different wavelengths of light refract by slightly differing amounts, which is why prisms can spread white light into a rainbow.

Answer: Buoyancy

Ships float because of buoyancy, a principle described by (checks notes) a Mr. Archimedes more than two thousand years ago. An object placed in a fluid experiences an upward force equal to the weight of the fluid it displaces. If that upward force is equal to or greater than the object's weight, the object floats instead of sleeping with the fishes.

A ship can be extremely heavy, but it is also large and full of air. This allows the ship to displace a great deal of water. When the weight of the displaced water matches the weight of the ship, equilibrium is achieved! The ship keeps everyone onboard safe and dry.

This explains why a solid steel block sinks while a steel ship floats. Shape matters, and hollow shapes are doing a lot of heavy lifting here.

Answer: Sound wave

Sound waves are mechanical waves. They need particles to shove around to move. In air, sound travels as a series of compressions and rarefactions.

That's an ugly way to say air particles bunch up or spread out as the wave goes through them.

And THAT is an ugly way of saying air molecules bump each other around to pass the wave along. Take away the particles, sound has no particles to aggravate, like a bully in an empty school playground.

The requirement of a medium is why sound behaves so differently in air, water, and solids. Sound travels faster in water than in air, and even faster in solids, because the particles are closer together and transmit those good vibrations more efficiently.

Answer: False

Um... no. Even though astronauts experience weightlessness on board the International Space Station, objects still have mass, and that's all inertia cares about. That is to say, my cat may be weightless in space, but it's still fat.

A one-ton object would have a huge amount of inertia, meaning it would still be reluctant to start or stop its motion just because you're in freefall and put on a baseball glove. You might be able to nudge it slightly if you're lucky, but if you call that playing catch, you're definitely a glass-half-full kind of person.

The point is, weightlessness does not mean masslessness. Gravity is still very much present on the space station. However, it's in orbit. That means everything in the station (and the station itself) is in continuous free fall around Earth. This creates the sensation of weightlessness while leaving all the usual laws of motion intact. Newton is still very much in charge, even if you're doing tumbles in the air.

Answer: Mass

Mass is a measure of how much matter an object contains, and it doesn't care where the object in question happens to be. On Earth, on the Moon, in orbit, or just a-bobbin' through interstellar space, an object's intrinsic mass stays the same. It is a fundamental property, basically a function of the number of atoms and subatomic particles the object contains.

People mix it up with weight all the time, but weight is a force. It depends on gravity and can change dramatically depending on location. It's an important distinction. As we learned in the previous question, just because something is weightless does not mean it's massless.

Mass plays a major role in physics, showing up everywhere you go. How hard is an object to push? Mass. How strongly does gravity pull on it? Mass. How hard is it to pick up? Mass. And then, of course, Einstein had a thing or two to say about mass and energy.

Answer: Friction

Friction is the force that resists motion when two surfaces slide against each other. It's the result of microscopic bumps and imperfections that catch and tug on each other as they scritch and scrape their way through the day. Even surfaces that look smooth to the naked eye are, at a smaller scale, a messy landscape of tiny obstacles slowing things down.

There are different types of friction, but sliding friction is the one at work here. It converts kinetic energy into heat, which is why rubbing your hands together makes them toasty when it's cold outside and why machinery needs lubrication, lest you end up with a still-smoking chunk of metal to take to the repair shop.

Friction is a nuisance and a necessity. On the downside, it screws up efficiency. On the plus side? Well, you wouldn't be able to walk or drive, and setting an object down on a table would be a heck of an adventure!

Answer: Solids are denser and stiffer

When my wife shouts from the other room, "Where are the GOOD scissors?", that sound of impending doom travels as a mechanical vibration, passing energy from particle to particle, until it causes my ear drums to vibrate and my mind to panic.

With rare exceptions, the particles in solids are tightly bound and strongly connected. That's a long-winded way of saying that solids tend to be stiff. That stiffness allows vibrations to be transmitted quickly and very efficiently, so sound moves faster even though the material is denser than a gas.

The speed of sound depends on both density and elasticity. While higher density alone would slow sound down, stiffness has the opposite effect. This stiffness in solids is vastly greater than that of gases, overwhelming the influence of density. The particles snap back into place rapidly after being disturbed, passing the vibration along like a juicy rumor in a room full of gossips.

This is why you can sometimes hear a distant train sooner by putting your ear to a rail, and why underwater sound travels farther and faster than in air.

(To complete the story, I honestly have no idea which pair is the "good scissors".)

Answer: Scattering of shorter wavelengths of sunlight

The sky is not blue. Okay. The atmosphere is not INHERENTLY blue. You can see the stars at night on a field of black, after all. Something's going on during the day.

That blue color of the daytime sky is caused by the scattering of sunlight by all the particles in Earth's atmosphere. Sunlight is white, containing all visible wavelengths, but shorter wavelengths like blue and violet, are scattered more efficiently when light interacts with all those tiny gas molecules in the air on its way to your retina.

This process is known as Rayleigh scattering, and it sends blue light a-bobbin' around the sky in all directions, making it appear blue no matter where you look. (Write that down for the next time your kid asks you.)

Although violet light is scattered even more than blue light, our eyes are less sensitive to violet, and some of it is absorbed by the upper atmosphere. The Sun also emits slightly more blue light than violet (it's a long story involving the temperature of the Sun at its surface), so no violet sky for you. From a strict branding perspective, I'm definitely Team Blue on this one.

This same scattering effect explains why sunsets and sunrises are often red or orange. When the Sun is low on the horizon, its light travels through much more atmosphere (it's going the long way: through the atmosphere AND across the sky just for you). Most of the blue light gets scattered away before it reaches your eyes, leaving behind the longer wavelengths like red and orange. The sky is still doing the same physics, just with a little more panache.

Answer: It increases

When a sound is heading toward you, the sound waves in front of it get compressed. Each successive wave crest is emitted from a position slightly closer to you than the last one, so the waves arrive more frequently. This increases the frequency of the sound, which your ears interpret as a higher pitch. This is the Doppler effect in action.

You hear this all the time, even if you never knew the name. A passing siren sounds higher-pitched as it approaches and suddenly drops in pitch as it passes and moves away. The sound itself does not change at the source, but your perception does because the spacing of the waves reaching you keeps changing.

And of course, the Doppler effect applies to all types of waves, not just sound. For example, light waves experience the effect (often called blueshift and redshift), which astronomers use to determine whether stars and galaxies are moving towards us or away from us. In this case, it's not pitch but color, red taking the place of lower pitch and blue taking the place of higher pitch.