A ballet dancer spins with 2.4 rev/s with her arms outstretched, when the moment of inertia about axis of rotation is 1 .With her arms folded, the moment of inertia about the same axis becomes 0.61 . calculate the new rate of spin.

Correct question is;

A ballet dancer spins with 2.4 rev/s with her arms outstretched,when the moment of inertia about axis of rotation is I. With her arms folded,the moment of inertia about the same axis becomes 0.6I about the same axis. Calculate the new rate of spin.

4 rev/s

Explanation:

We are given;

Initial Angular velocity; ω_i = 2.4 rev/s

Initial moment of inertia; I_i = I

Final moment of inertia; I_f = 0.6I

From conservation of angular momentum, we have;

I_i × ω_i = I_f × ω_f

Where ω_f is the new rate of spin.

Thus, let's make it the subject to get;

ω_f = (I_i × ω_i/I_f)

Plugging in relevant values, we have;

ω_f = (I × 2.4/0.6I)

I will cancel out to give;

ω_f = 2.4/0.6

ω_f = 4 rev/s

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

its c i just checked it