- #1
penutbutr
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Homework Statement
Calculate the energy needed for 1 kg mass at the velocity of 2 m/s go up to the velocity of 6 m/s.
Homework Equations
Ek = mv2/2
The Attempt at a Solution
From the mass point of view, it is stationary and goes up to a velocity of delta (6-2) m/s = 4 m/s
so the energy needed must be Ek = 1*42/2 J = 16/2 J = 8 Joules
But the answer is 16 Joules.
Ebefore = 1*22/2 = 4/2 Joule = 2 Joule
Eafter = 1*62/2 = 36/2 Joule = 18 Joule
Edelta= Eafter-Ebefore = (18-2) Joules = 16 Joules
How can the answer not be 8 Joules? From the mass perspective, it is stationary and just goes up 4 m/s.