You have a helicopter, whose rotating blades can all be approximated as long thi

Question

You have a helicopter, whose rotating blades can all be approximated as long thin rods rotating around one end.

Your helicopter has 6 identical blades, each of mass 26.4 kg and length 4.7 m.

What is the total moment of inertia of the helicopter blades?

During a very quick stop, a car decelerates at 3.9 m/s2. How many revolutions do the tires make before coming to rest, if the initial angular velocity is 36.8 rad/s? The tires each have a radius of 0.6 m.

If the angular momentum of an ice skater is 3.16 kg m2/s, and the skater is spinning with an angular speed of 5.75 rad/s, what is the skater's moment of inertia?

Explanation / Answer

I = 6 * 1/3 ML2 = 2 * 26.4 * 4.7*4.7 =1166.35 Kg.m2

b) we know that final angular velocity Vr2 = Ur2 + 2arSr

given that Ur = 36.8 rad/s and ar = a*r = 3.9*0.6 = 2.34

we know at stop Vr =0 so Sr =289.36 radiun

c) we know that L = Iw given L = 3.16 kg m2/s and w = 5.75 rad/s

so I = L/w = 3.16/5.75 = 0.5495 Kg. m2

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