Difference between revisions of "Unit"
(Created page with "== Speed == Common outside of physics: mph, kph. Common inside of physics: m/s Conversions: * 1m/s = 2.24 mph * 1 mph = 0.447 m/s Common values: * Slow walk: 1 m/s * Bris...") |
(No difference)
|
Latest revision as of 14:46, 30 April 2012
Speed
Common outside of physics: mph, kph.
Common inside of physics: m/s
Conversions:
- 1m/s = 2.24 mph
- 1 mph = 0.447 m/s
Common values:
- Slow walk: 1 m/s
- Brisk walk: 3 m/s
- Run: 5 m/s
- Sprint: 8 m/s
- Fastest man on earth: 10 m/s
- Car at city speeds: 35 mph = 15 m/s
- Car at highway speeds: 60 mph = 30 m/s
- Commercial airliner: 570 mph = 250 m/s
- Speed of sound: mach 1 = 340 m/s = 760 mph
- Jet Fighter (F-22) at Top Speed: mach 1.85 = 1,400 mph = 630 m/s
- Sniper rifle bullet speed: 860 m/s = 1,900 mph
- Speed of a satellite in geo-synchronous orbit: 3.07 km/s = 6 900 mph
- Earth's escape velocity: 1.21x10^5 m/s = 250 000 mpg
- Speed of light: 299 792 458 m/s (exactly) = 3.00x10^8 m/s = 6.70 x 10^8 mph
Energy
Physicists have too many ways to count energy.
I like to use the kinetic energy of a bullet, a car, and a train to illustrate how mass plays a role.
A bullet weighs about 200 grams. A car weighs about 1 000 000 g, and a train engine about 6.4 x 10^8 g.
Speed | 1/2 v^2 | Ke bullet (m = 10^2g) | Ke human (10^5g) | Ke train (m=10^9g) | |
---|---|---|---|---|---|
0 m/s | 0 J | 0 J | 0 J | 0 J | 0 J |
2 m/s (walking) | 1 J/g | 2x10^2 J | 2x10^5 J | 2x10^6 J | 2x10^9 J |
5 m/s (jogging) | 10 J/g | ||||
10 m/s (fastest man on earth) | 50 J/g | ||||
15 m/s (city speeds) | 100 J/g | ||||
45 m/s (very fast car) | 1000 J/g
At this speed, bullets have as much Ke as a human walking. | ||||
150 m/s (slow airplane) | 10 000 J/g
At this speed, humans have as much Ke as a train walking, bullets have as much Ke as a human jogging. | ||||
450 m/s (bullets / sound) | 100 000 J/g
At this speed, humans have as much Ke as a train jogging. | ||||
1400 m/s (SR-71) | 1 000 000 J/g | ||||
4500 m/s | 10 000 000 J/g
At this speed, bullets have as much Ke as a train walking. | ||||
14 000 m/s (geo-stationary orbit) | 100 000 000 J/g | ||||
45 000 m/s (escape velocity on earth) | 1 000 000 000 J/g |