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Homework Statement
A 50g object is moving east at 0.3 m/s. A 100g object is moving east as well at 0.25 m/s. These objects have an inelastic collision.
a) Find their final velocity
b) Find the kinetic energy lost
Homework Equations
P1 + P2 = P3 + P4 ; momentum is conserved
Ek = 1/2 mv^2
The Attempt at a Solution
So the only thing conserved is momentum
Please excuse me for not using units, it's too confusing to do that on a keyboard.
a) (0.3 * 50/1000 + 0.25 * 100/1000) / (150/1000) = vf = 4 / 15 m/s
b) Ek1 = 0.5 * (50/1000) * 0.3^2 + 0.5 * (100/1000) * 0.25^2 = 0.005375 J
Ek2 = 0.5 * (50/1000) * (4/15)^2 + 0.5 * (100/1000) * (4/15)^2= 0.00533333333J
Ek1 - Ek2 = 0.000042 J
Is this correct? Someone said that its Ek2 - Ek1 but that doesn't make sense to me, because then delta(Ek) would be negative and this is impossible. Also, 10 marbles - 3 marbles. 7 were lost