Water Copters
𝐹 = 𝑚 𝑎𝜕 𝑃
𝜕𝑡= 𝑚 𝑎
𝜕 𝑃
𝜕𝑡=0 ⟹ 𝑃 𝑧,𝜒 = 𝑃 𝑧,𝑎𝑖𝑟
𝑚𝜒𝑔 Δ𝑡 = 𝑚𝑎𝑖𝑟𝑣𝑎𝑖𝑟 = 𝜌𝑎𝑖𝑟𝐴𝜒𝑣𝑎𝑖𝑟 Δ𝑡 𝑣𝑎𝑖𝑟
𝑣𝑎𝑖𝑟2 =
𝑚𝜒𝑔
𝜌𝑎𝑖𝑟𝐴𝜒
Some reference
• 𝑣𝑤𝑎𝑡𝑒𝑟 = 6.5 𝑚𝑠𝑒𝑐 ~ 23 𝑘𝑚
ℎ𝑟
• 5K world record: 12:37.35 -> 𝑣𝑊𝑅 = 6.6 𝑚𝑠𝑒𝑐
• 800m ER: 1:41.91 -> 𝑣𝑊𝑅 = 7.92 𝑚𝑠𝑒𝑐
• 1000m WR: 2:11.96 -> 𝑣𝑊𝑅 = 7.57 𝑚𝑠𝑒𝑐
Water-Polo periods:
• 4 quarter game
• Each quarter = 8 minutes of actual play time.
• Time-outs: 2 minutes, 5 minutes half-time.
• 50-60 minutes of actual in-water time.
How much swimming is involved?
• Water polo swimming
• Swimming = Resting?!!
• At the MOST 30% of time.
Water polo violence