Answer:
155.5 rev/min
Explanation:
First, we will calculate the initial moment of inertia I_o. We will consider the ice skater as a rod rotating around its axis. Then, we calculate the final moment of inertia I_f. In this occasion we consider the arms as a rod of length L that is horizontally positioned, L so that the length of an arm is L/2. We will call M_1 the mass that remains close to the rotation axis (90 percent) and M_2 the mass located at the arms (10 percent). Finally, we write the equation for the conservation of angular momentum and we solve for ω_f.
I_o=MR^2/2
=(45)(0.15)^2/2
=0.5 kgm^2
M_1=(0.9)(45)
=40.5 kg
M_2=(0.1)(45)
=4.5 kg
I_f=M_1*R^2/2+M_2*L^2/12
=1.1 kg m^2
I_f*ω_f=I_o*ω_o
ω_f = I_o*ω_o/ I_f
=155.5 rev/min
For this case you must first know the definition of density. D = m / v where, m: mass v: volume. You can then write the following hypothesis: IF you know two physical characteristics of an object then you can determine the density. First weigh the object, THEN measure its volume BECAUSE the density is the quotient between the mass and the volume of an object.
The current applied is 90A.
The formula used is I =Q/t.
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