- #1
LesterTU
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Homework Statement
A 30-kg child is on a rotor ride at a carnival. The radius of the rotor is 3 m and it completes 0.4 revolutions in one second. The coefficient of static friction is 0.6. What is the magnitude of the child's apparent weight?
Homework Equations
ΣFx : FN = mv2/r
ΣFy : Ff = Fg
The Attempt at a Solution
First I need to find v:
0.4 revolutions per second is equivalent to one revolution per 2.5 s, so T = 2.5 s.
v = 2πr / T => v = 7.54 m/s.
Since the apparent weight is the magnitude of the resultant force exerted on a body by a supporting surface, the way I see it FN is the only force that fits this description so I figured
apparent weight = FN = mv2/r = 568.5 N.
However the solution given by the author says that
apparent weight = (FN2 + Fg2)1/2 = 640 N.
I've been trying to understand why mg plays a role in the child's apparent weight but I don't see how in this case