Unit

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