Asked by Bill
A father racing his son has one-third the kinetic energy of the son, who has two-fifths the mass of the father. The father speeds up by 1.5 m/s and then has the same kinetic energy as the son.
What is the Father's initial speed?
What is the Son's initial speed?
What is the Father's initial speed?
What is the Son's initial speed?
Answers
Answered by
drwls
Let the father's mass be M sos that the son's mass must be 2M/5. Let the father's initial speed be V, and the son's v.
(1/2)MV^2 = (1/3)(2M/5)v^2
which leads to
V^2 = (4/15)v^2
(1/2)M(V +1.5)^2 = (2M/5) v^2
V^2 + 3V + 2.25 = (4/5) v^2
3V^2 = (4/5)v^2
Now you can eliminate v.
2V^2 -3V -2.25 = 0
That can be solved for a positive V using the quadratic equation. Chack my math.
(1/2)MV^2 = (1/3)(2M/5)v^2
which leads to
V^2 = (4/15)v^2
(1/2)M(V +1.5)^2 = (2M/5) v^2
V^2 + 3V + 2.25 = (4/5) v^2
3V^2 = (4/5)v^2
Now you can eliminate v.
2V^2 -3V -2.25 = 0
That can be solved for a positive V using the quadratic equation. Chack my math.
Answered by
Neal
This answers skips too many steps. It is not helpful.
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