Question Number 29464 by NECx last updated on 09/Feb/18
$${An}\:{arrow}\:{is}\:{projected}\:{straight} \\ $$$${upwards}\:{at}\:{a}\:{speed}\:{of}\:\mathrm{100}{m}/{s}. \\ $$$${With}\:{what}\:{speed}\:{will}\:{it}\:{return}\:{to} \\ $$$${the}\:{ground}\:{if}\:{air}\:{resistance}\:{is} \\ $$$${ignored}? \\ $$
Answered by mrW2 last updated on 09/Feb/18
$${the}\:{arrow}\:{has}\:{the}\:{same}\:{kinetic}\:{energy} \\ $$$${when}\:{it}\:{returns}\:{to}\:{the}\:{starting}\:{point}, \\ $$$${i}.{e}.\:{it}\:{has}\:{the}\:{same}\:{speed}\:{as}\:{it}\:{left} \\ $$$${that}\:{point}. \\ $$$$\Rightarrow{v}=\mathrm{100}\:{m}/{s} \\ $$