# Physics Test - how smart are you?

Ramned
Posers and Puzzles 06 Jun '07 20:08
1. Ramned
The Rams
06 Jun '07 20:082 edits
Here are some questions to see not only if you know physics, but if you have common sense ðŸ˜‰

Level Easy
1. Assuming no air resistance, which falls faster, a penny or a feather?
2. True or False: Energy cannot be created or destroyed, but it can be converted to different forms of energy.
3. Carl has a mass of 20 kg on Mars. Assuming gravity is 10 meters per second on earth, what is his mass on Earth?
4. Why is the sky blue?
5. When you are trying to point a red laser light on a fish in the water, where should you aim: Above the fish, on the fish, or below the fish?

If I see someone get 4/5 of those, I will post harder questions, until I stump you (or you answer everything correctly to the point I am stumped.)
2. agryson
AGW Hitman
06 Jun '07 20:15
Originally posted by Ramned
Here are some questions to see not only if you know physics, but if you have common sense ðŸ˜‰

[b]Level Easy

1. Assuming no air resistance, which falls faster, a penny or a feather?
2. True or False: Energy cannot be created or destroyed, but it can be converted to different forms of energy.
3. Carl has a mass of 20 kg on Mars. Assuming gravity is 10 ...[text shortened]... he fish, or below the fish?

If I see someone get 4/5 of those, I will post harder questions.[/b]
1: They both fall at the same speed.
2: True. (If we include mass/energy conversion as a 'form of energy'ðŸ˜‰
3: 20kg but his weight is a whopping 200kg
4: Two reasons, refraction of light from the less dense medium of space to the more dense medium of the atmosphere (hence it turns more reddish at dawn and dusk) second reason is that the absorption spectra of Nitrogen and Oxygen are lower in the blue part of the spectrum, letting more blue light through.
5: On the fish, because the image of the fish you see is being refracted by the same amount as the laser light will be. (but actually you are aiming above the fish and the light bends down, you just can't see that from your vantage point.)
3. Ramned
The Rams
06 Jun '07 20:21
Originally posted by agryson
1: They both fall at the same speed.
2: True. (If we include mass/energy conversion as a 'form of energy'ðŸ˜‰
3: 20kg but his weight is a whopping 200kg
4: Two reasons, refraction of light from the less dense medium of space to the more dense medium of the atmosphere (hence it turns more reddish at dawn and dusk) second reason is that the absorption spectra ...[text shortened]... ng above the fish and the light bends down, you just can't see that from your vantage point.)
Very nice on number 5 - that was tricky, you had to think about the spectator's view of the fish.

You got at least 4/5. On why the sky is blue...you told me something I wasn't looking for.

So, maybe this works: Why is a white shirt white? Why is fire reddish-orange? Why are elephants grey? Use 1 principle to explain all of those...(hint - light.)
4. 06 Jun '07 20:26
I made the 5 questions quite correctly.
5. irontigran
Rob Scheider is..
06 Jun '07 20:27
i counted down the numbers...ðŸ˜‰
6. agryson
AGW Hitman
06 Jun '07 20:28
Well, a fire is slightly different to the others, the elephant and the shirt reflect light, so it's reflection. The white shirt reflects all visible colours, so appears white. The grey elephant reflects all visible colours, but also absorbs a certain proportion of all visible colours, reducing the saturation, thus it's grey.
The flame is technically emission, which is a different process, got to do with the energy of the chemical reaction (C + O2 -> CO2) which translates into a photon in the yellow/red part of the spectrum.
All processes have got something to do with emission and absorbance spectra.
7. Ramned
The Rams
06 Jun '07 20:344 edits
Originally posted by Ramned
So, maybe this works: Why is a white shirt white? Why is fire reddish-orange? Why are elephants grey? Use 1 principle to explain all of those...(hint - light.)
Keep thinking about that. Edit - you got it ðŸ™‚

Next Set
1. Which has more kinetic energy: A 50 kg truck moving at 20 m/s, or a 25 kg truck moving at 40 m/s?
2. Why can no animal hear sound waves in outer space?
3. When a police car with sirens beeping comes toward you, the police in the car hears the siren and so do you. What is the difference between the pitches that the policeman hears and you hear? Why the difference?
4. What is the name of the phenomena illustrated in question 3?
5. What is the standard unit for weight?

Get 4/5 and I'll get them more challenging - next set 10 questions.
Note, m/s = meters per second
8. AThousandYoung
All My Soldiers...
06 Jun '07 20:402 edits
Originally posted by Ramned
Here are some questions to see not only if you know physics, but if you have common sense ðŸ˜‰

[b]Level Easy

1. Assuming no air resistance, which falls faster, a penny or a feather?
2. True or False: Energy cannot be created or destroyed, but it can be converted to different forms of energy.
3. Carl has a mass of 20 kg on Mars. Assuming gravity is 10 ...[text shortened]... der questions, until I stump you (or you answer everything correctly to the point I am stumped.)[/b]
1. Neither
2. True, assuming matter is considered "another form of energy".
3. 20 kg
4. Red and blue light act differently in the air. Blue light is scattered by the molecules in the air and red light is not. Any place in the sky where the Sun is not is providing indirect light. This light is blue light that has been redirected from it's original direction and is now aiming at you, while the red light is not redirected and so you only get red light directly from the Sun which you can't look at anyway.
5. Below.

EDIT - Oops, missed #5. I think.
9. agryson
AGW Hitman
06 Jun '07 20:41
Originally posted by Ramned
Keep thinking about that. Edit - you got it ðŸ™‚

[b]Next Set

1. Which has more kinetic energy: A 50 kg truck moving at 20 m/s, or a 25 kg truck moving at 40 m/s?
2. Why can no animal hear sound waves in outer space?
3. When a police car with sirens beeping comes toward you, the police in the car hears the siren and so do you. What is the difference b ...[text shortened]... 4/5 and I'll get them more challenging - next set 10 questions.
Note, m/s = meters per second[/b]
1: The have the same kinetic energy
2: sound needs a medium in which to travel, unlike light.
3: The frequency of sound heard by you will be higher than that heard by the policeman in the car.
4: Doppler effect.
5: Hmm... Kilogram, though technically, it's Kgms-²
10. 06 Jun '07 20:41
Originally posted by agryson
1: They both fall at the same speed.
2: True. (If we include mass/energy conversion as a 'form of energy'ðŸ˜‰
3: 20kg but his weight is a whopping 200kg
4: Two reasons, refraction of light from the less dense medium of space to the more dense medium of the atmosphere (hence it turns more reddish at dawn and dusk) second reason is that the absorption spectra ...[text shortened]... ng above the fish and the light bends down, you just can't see that from your vantage point.)
20kg but his weight is a whopping 200kg

Newtons (N) is the unit for weight, not kilograms (kg), which is for mass.
You lost a mark...
11. AThousandYoung
All My Soldiers...
06 Jun '07 20:411 edit
Originally posted by Ramned
Very nice on number 5 - that was tricky, you had to think about the spectator's view of the fish.

You got at least 4/5. On why the sky is blue...you told me something I wasn't looking for.

So, maybe this works: Why is a white shirt white? Why is fire reddish-orange? Why are elephants grey? Use 1 principle to explain all of those...(hint - light.)
Those objects reflect the wavelengths of light that your eyes and brain see as those colors.

Except fire. It actually emits those wavelengths.
12. agryson
AGW Hitman
06 Jun '07 20:432 edits
Mass by acceleration, you're absolutely right, I was thinking force, which of course weight is.

Edit... but 9 out of 10 ain't bad.
Edit Edit ok, then 8, still a first! Better than I did in my finals!
13. Ramned
The Rams
06 Jun '07 20:451 edit
Originally posted by agryson
1: The have the same kinetic energy
2: sound needs a medium in which to travel, unlike light.
3: The frequency of sound heard by you will be higher than that heard by the policeman in the car.
4: Doppler effect.
5: Hmm... Kilogram, though technically, it's Kgms-²
Ay, you missed 2. (But you did get the sky is blue question - ROYGBIV. You see colors that are reflected, not absorbed - good.)

#1 , #5.

Someone answered #5 - weight is in Newtons.

If someone can answer #1 correctly (and explain since there are only 2 choices) I will put 10 even harder ones up right now.
14. AThousandYoung
All My Soldiers...
06 Jun '07 20:461 edit
Originally posted by Ramned
Keep thinking about that. Edit - you got it ðŸ™‚

[b]Next Set

1. Which has more kinetic energy: A 50 kg truck moving at 20 m/s, or a 25 kg truck moving at 40 m/s?
2. Why can no animal hear sound waves in outer space?
3. When a police car with sirens beeping comes toward you, the police in the car hears the siren and so do you. What is the difference b ...[text shortened]... 4/5 and I'll get them more challenging - next set 10 questions.
Note, m/s = meters per second[/b]
1. The 25 kg truck. 0.5 x 25 x 40^2 = 20,000 J. 0,5 x 50 x 20^2 = 10,000 J. K = 1/2 x mv^2
2. Sound waves are carried by the air and there is no air in space.
3. I hear a higher pitch than the cop. The pitch depends on the distance between the sound waves, and because the car is approaching the later waves are emitted closer to me than they otherwise would be and the waves are therefore closer together.
4. Doppler Effect.
5. Newton.
15. Ramned
The Rams
06 Jun '07 20:48
Originally posted by AThousandYoung
1. The 25 kg truck.
2. Sound waves are carried by the air and there is no air in space.
3. I hear a higher pitch than the cop. The pitch depends on the distance between the sound waves, and because the car is approaching the later waves are emitted closer to me than they otherwise would be and the waves are therefore closer together.
4. Doppler Effect.
5. Newton.
Good - #2 - it is a medium, not air necessarily, but you're right.

Explain why on #1.