Tagged Questions

-3
votes
3answers
71 views

Speed of an object in air versus in vacuum

Okay, imagine that you are shooting a rocket down a tunnel that is 60 miles long and the rocket is travelling at 60mph, so the rocket should reach the end of the tunnel in a hour, right? Yep, in an ...
1
vote
1answer
87 views

Weightlessness on Earth

Would the following work? Imagine one would 1) create a straight 4000 km long tube (at ground level), following the curvature of the Earth, wide enough to hold a pod the size of an aircraft cabin; ...
0
votes
0answers
26 views

Intuitive understanding of the equation for kinetic energy [duplicate]

Possible Duplicate: Why does kinetic energy increase quadratically, not linearly, with speed? I know this is one of the easiest equations out there and I've used it for years but its still ...
4
votes
4answers
2k views

How Felix Baumgartner has reached the speed of sound quickly

I have watched Felix Baumgartner freefall; but I wonder how Felix has reached the speed of sound quickly, in a matter of some seconds, then we had no idea of its speed? Any explanation please.
2
votes
3answers
516 views

Why would a fat skydiver fall first in free fall?

I was having one of those obnoxious conversations with a friend where he was arguing that a fat skydiver would reach the ground faster than a skinny skydiver. To me it seemed as obvious that the world ...
-1
votes
1answer
127 views

What is the quantity in physics that is advanced from speed? [closed]

What is the quantity in physics that is advance from speed? i know one is velocity, one is speed, one is acceleration.
3
votes
3answers
837 views

Does friction decrease as objects move faster against each other?

I was told that the faster two objects move against each other, the less the friction between them would be… compared to if they were moving slower. In physics class, we always use the coefficient of ...
-2
votes
2answers
3k views

How exactly does mass affect speed?

I konw that mass affects weight (force), so how does that relate to speed? F=ma. so how does all this affect speed?
37
votes
14answers
7k views

Why does kinetic energy increase quadratically, not linearly, with speed?

As Wikipedia says: [...] the kinetic energy of a non-rotating object of mass $m$ traveling at a speed $v$ is $mv^2/2$. Why does this not increase linearly with speed? Why does it take so much ...