Squids and octopuses propel themselves by expelling water. They do this by keepi

Question

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 6.50kgsquid (including the water in the cavity) at rest suddenly sees a dangerous predator.

Part A

If the squid has 1.65kg of water in its cavity, at what speed must it expel this water to instantaneously achieve a speed of 2.70m/s to escape the predator? Neglect any drag effects of the surrounding water.

Part B

How much kinetic energy does the squid create by this maneuver?

Explanation / Answer

A) let v is the speed of water

Apply conservation of momentum

1.65*v = (6.5-1.65)*2.7

v = (6.5-1.65)*2.7/1.65

= 7.94 m/s <<<<<<<----------Answer

B) kinetic enrgy created = 0.5*1.65*7.94^2 + 0.5*(6.5-1.65)*2.7^2

= 69.7 J <<<<<<<----------Answer

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