BIO Animal Propulsion.? Squids and octopuses propel themselves by expelling water. They do this by keeping water in a cavity and then suddenly contracting the cavity to force out the water through an opening. A 6.50-kg squid (including the water in the cavity) at rest suddenly sees a dangerous predator. (a) If the squid has 1.75 kg of water in its cavity, at what speed must it expel this water suddenly to achieve a speed of 2.50 m/s to escape the predator? Ignore any drag effects of the surrounding water. (b) How much kinetic energy does the squid create by this maneuver?
Solution 19E a) Step 1: The initial velocity of the squid was zero as it was at rest. Mass of squid with water is 6.50 kg. Amount of water present inside it’s cavity was 1.75 kg. So, the mass of the squid without water is, 6.50 1.75 = 4.75 kg . It has to achieve a velocity of 2.50 m/s suddenly, which can be done by releasing the water at some speed.