[loeg]

Energy is proportionate to the square of velocity. So it's:

Walking: 5 km/h * 70kg => 875 (although this is a very slow estimate for a walker) (please ignore the non-canonical units)

e-bike: 20 km/h * 90 kg => 18,000 (I think your estimate for ebike mass might be on the low side at 20kg, but whatever)

car: 50 km/h * 2000kg => 2,500,000 (and that's a fairly low speed for cars! Drunk drivers often drive faster than is wise.)

Everything else is a rounding error compared to the energy of a car.

[uoaei]

Realistic estimates:

Walking: 6kph, 70kg => 100J (0.02% of car)

Analog bike: 18kph, 80kg => 2kJ (0.36% of car)

E-bike: 25kph, 100kg => 4.6kJ (0.82% of car)

Car: 50kph, 2000kg => 560kJ (100% of car)

[loeg]

Thanks. Just for the sake of fleshing out the speeding angle:

Car, 64 kph => 164% of car at 50 kph

Car, 110 kph => 480% of car at 50 kph

[Someone]

> Walking: 5 km/h * 70kg => 875 (although this is a very slow estimate for a walker)

In the context of this thread (a walker who’s drunk), I don’t think it’s very slow.

Also, https://en.wikipedia.org/wiki/Preferred_walking_speed:

“The preferred walking speed is the speed at which humans or animals choose to walk. Many people tend to walk at about 1.42 metres per second (5.1 km/h; 3.2 mph; 4.7 ft/s).”

https://www.sciencedirect.com/science/article/pii/S209575641...:

“The results show teenagers walk at an average speed of 1.45 m/s, young adults walk at an average speed of 1.55 m/s, middle age pedestrians walk at a speed of 1.45 m/s, older pedestrians walk at speed of 1.09 m/s, and elderly or physically disabled pedestrians walk at a speed of 1.04 m/s.”

5km/hour is about 1.4m/s; the fastest of these speeds is 5.6 km/hour.

[codethief]

Initial kinetic energy is not the right physical quantity to look at. Most of that kinetic energy will remain in the car/bike/…, i.e. it doesn't tell you much about how much energy will get transferred to the victim – it merely gives you a bound from above.

More details: https://news.ycombinator.com/item?id=35233887