An astronaut in a space suit is motionless in outer space. The propulsion unit strapped to her back ejects some gas with a velocity of magnitude 40.0 m/s. The astronaut recoils with a velocity of 1.00 m/s in the opposite direction. If the mass of the astronaut and space suit after the gas is ejected is 100 kg and the mass of the gas ejected is 2.50 kg, then the total kinetic energy is
A) 2,050 J.
B) 3,430 J.
C) 4,150 J.
D) 5,070 J.
E) 6,320 J.

Question

Quizplus · Accepted Answer

The total kinetic energy is the sum of the kinetic energies of the astronaut and the ejected gas. The kinetic energy of the astronaut is (1/2) * 100 kg * (1.00 m/s)^2 = 50 J. The kinetic energy of the gas is (1/2) * 2.50 kg * (40.0 m/s)^2 = 2,000 J. Therefore, the total kinetic energy is 50 J + 2,000 J = 2,050 J.

An Astronaut in a Space Suit Is Motionless in Outer