Question

Some species of jellyfish use jet propulsion to get around, a much gentler form of jet propulsion than squid use. A small jellyfish takes water into its bell; the total mass of jellyfish and water is 3.2 g. It then rapidly ejects 1.3 g of water, achieving a speed of 0.070 m/s. What is the speed of the ejected water?

Answer 1

Answer:

speed of ejected out water will be 0.102 m/s

Explanation:

Initially the jellyfish is given at rest

so here since there is no external force on the system of jelly fish and the water in it so the momentum of the whole system will remains conserved

so here we have

$P_i = 0$ initial momentum is zero

now final momentum of both will also be zero

so here we have

$m_1v_1 + m_2v_2 = 0$

$m_1= 1.3 g$

$m_2 = (3.2 - 1.3) = 1.9 g$

$v_2 = 0.070 m/s$

so we have

$(1.3g)(v_1) + (1.9 g)(0.070) = 0$

$v_1 = 0.102 m/s$

so speed of ejected out water will be 0.102 m/s