Linked Questions

1
vote
1answer
62 views

How can astronauts rotate their body in empty space ? How do they undergo “angular displacement” without any external torque? [duplicate]

How does the astronaut in the following video do what he is doing ? https://youtu.be/7ZPVg3qD07g?t=145 This question is kind of a follow up to Why don't we ever see astronauts on space walks ...
1
vote
0answers
69 views

Can an astronaut in free space turn his head without moving the rest of his body in opposite direction? [duplicate]

Can an astronaut in free space turn his head without moving (turning) the rest of his body (and also not moving hands or legs) in opposite direction?
24
votes
14answers
24k views

Is it possible to walk in a friction-less world?

Is it possible to walk in a frictionless world. I think you won't be able to walk because walking depends on friction acting on your feet. I think about it like an ice rink because when you try to ...
42
votes
5answers
2k views

Intuition as to why the orientation (of a 3D object) is not a conserved quantity?

Say you start off floating in space, in a fixed position and orientation, with zero linear and angular velocity, with no external forces. So you are a closed mechanical system. By twisting your body ...
14
votes
8answers
16k views

What is a rocket engine thrusting against in space?

I know Newton's third law of motion might be the answer for this but still I am wondering how the rockets could thrust in the empty space and move in the opposite direction. I guess an astronaut ...
13
votes
3answers
4k views

Changing Rotation Direction in Mid Air

Not sure whether this is an appropriate question for this site, but could anyone explain the physics behind how this skier is able to change his direction of rotation mid-air? https://www.youtube.com/...
7
votes
7answers
2k views

What happens to our force when we walk on ice?

I'm scratching my head a lot in trying to understand friction. So far I understand that "without friction we would not be able to walk". But that sounds really vague and unclear, so much in ...
3
votes
3answers
17k views

What happens to photons after they hit objects?

If I am not wrong when light hits for example white wall most of the photons are absorbed and transformed into heat and few of the photons at certain wavelength are reflected from the object. So white ...
8
votes
2answers
734 views

Would a sneeze by a cosmonaut in a spacesuit affect his movement?

Naive question; feel free to shoot me down It is a truism that any motion in space would continue indefinitely unless it is opposed by an external force. If a cosmonaut were to sneeze within his/her ...
14
votes
1answer
2k views

Effect of the tail of the cat in the falling cat problem

To explain why a falling cat can turn by 180 degree without external torque and without violation of the conservation of angular momentum, one usually models the cat as two cylinders as in http://en....
7
votes
2answers
3k views

When falling through the air, does swinging arms/legs actually help anything?

Let's say someone jumps off an Olympic-sized diving board into a pool below (so air resistance is negligible). As soon as they jump, they start swinging their arms. Does this help them stay upright ...
5
votes
1answer
347 views

Is it possible to rotate an angle on perfectly smooth ice?

You must start and end with the same pose. Prove it if you think you can't.
2
votes
1answer
1k views

How does a tightrope walker return to equilibrium?

I do not understand how tightrope walkers return themselves to equilibrium. I am not concerned with the direction along the rope or wire where their base can be large, and they are able to move their ...
1
vote
1answer
1k views

Mechanics of a falling cat [duplicate]

It is a general statement that cats tend to fall on their feet. How far is this is a valid statement? If I were to drop a cat from 50 meters height, feet up(hypothetically), would it still land on ...
1
vote
2answers
413 views

Can a system's internal forces change the system's motion?

Let say the motor makes the two rigid body rotate as a same velocity. (they rotate the opposite direction) then the Net force of the motor is 2Fsin(Theta). The acceleration of the motor is 2Fsin(theta)...

15 30 50 per page