Remarkably, in the intervening 20 years since I took high school physics I have not killed the brain cell remembering that gravitational acceleration on Earth is 9.8m s/2. Guangyuan, China resident Yunzhi Ziao is intimately familiar with gravity as a practical matter as he was struck in the head with a knife while taking a walk last week. Unlike many Chinese stabbings, it wasn’t an attack by Uighur Separatists. Instead, a “Mr. Wu” who lived in the apartment whose balcony Ziao happened to be walking by told police that he had left the knife in a flower pot and the wind blew it over.
“It hurt a lot,” Xiao told NBC News from his hospital bed. “I cried out, ‘My head! My head hurts!’ but I did not know what had happened.” A street vendor shouted at Xiao, “There is a knife in your head!” He managed to walk another 100 yards before the pain became too much and he was forced to sit down at a phone booth. “Some warm-hearted people passing by saw me bleeding and called the police who took me to a traditional Chinese medicine hospital,” Xiao added. “A few hours later doctors took the knife out of my head.”
According to the UK Telegraph, the balcony of the High-rise apartment was 8 stories high. Assuming a height of 3m/story that would mean the knife was travelling at approximately 21.7 meters/s when it stuck Mr. Xiao. Or about 48.5 miles per hour for those of us here in the States. Ouch.(thanks www.gravitycalc.com – I was lazy).
Gravity is not just a good idea. It’s the law.