In: Physics
A uniform helicopter rotor blade is 8.97 m long, has a mass of 104 kg, and is attached to the rotor axle by a single bolt. (a) What is the magnitude of the force on the bolt from the axle when the rotor is turning at 329 rev/min? (Hint: For this calculation the blade can be considered to be a point mass at its center of mass. Why?) (b) Calculate the torque that must be applied to the rotor to bring it to full speed from rest in 7.68 s. Ignore air resistance. (The blade cannot be considered to be a point mass for this calculation. Why not? Assume the mass distribution of a uniform thin rod.) (c) How much work does the torque do on the blade for the blade to reach a speed of 329 rev/min?
sol:)
Given data
mass(m) = 104 kg
length (L ) = 8.97m
a.) Magnitude of the force:
convert revolution per minute in radians/ sec
above omega value substitute in magnitude force equation
Therefore, magnitude force exerted by the blade is 552.929*103 N
b.) Torque:
we know that the torque formula is
given time (t) = 7.68 s
Hence, torque exerted by the rotor is 12.50*103 N.m
c.) Workdone
we know that workdone formula is
given 329 rev/min
convert rpm to rad /s