Helicopter rotor has four blades

  • Thread starter Thread starter Whatupdoc
  • Start date Start date
  • Tags Tags
    Helicopter Rotor
AI Thread Summary
The discussion focuses on calculating the linear speed of a helicopter rotor blade with a length of 3.90 meters and a rotational speed of 480 revolutions per minute. The correct formula to determine the linear speed is V = 2πR/T, where R is the blade length and T is the rotational speed. The calculations show that the distance traveled by the blade tip in one rotation is 24.5 meters, leading to a linear speed of 11760 meters per minute when factoring in the rotational speed. There is a consensus that the initial answer provided was incorrect, confirming the proper calculation method. Understanding these calculations is crucial for accurate aerodynamic assessments in wind tunnel experiments.
Whatupdoc
Messages
99
Reaction score
0
A model of a helicopter rotor has four blades, each of length 3.90m from the central shaft to the blade tip. The model is rotated in a wind tunnel at a rotational speed of 480rev/min .

A.) What is the linear speed of the blade tip?

given
R= 3.9
T = 480

would it just be V= 2*pi*R/t
and got = .05105

someone helped me(not at this forum) and the answer is wrong. can someone help? isn't it just asking for the velocity?
 
Last edited:
Physics news on Phys.org
Well you say the rotational velocity is 480 rotations / minute
1 rotation at a distance R from the center is the cirumference of a circle, so the distance the tip travels in one rotation is : 2*Pi*Radius meters

D = 2*3.14159*3.90 = 24.5 meters

You say 480 Rot/Min => 480 (rotrotations/minute) * (24.5 meters/rotation) = 11760 meters per minute.
 


Yes, you are correct. The linear speed of the blade tip can be calculated using the formula V = 2πR/T, where V is the linear speed, R is the length of the blade, and T is the rotational speed in revolutions per minute (rev/min). Plugging in the given values, we get V = 2π(3.9)/480 = 0.05105 m/s. It is possible that the answer you were given is incorrect.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

[Mechanics] Friction decelerating a helicopter rotor assembly
Replies
1
Views
1K
Calculating Torque and Current for Quadcopter Rotor Blades
Replies
1
Views
1K
Acceleration of the tips of wind turbine blades
Replies
13
Views
5K
Motion in a circle of helicopter rotor
Replies
1
Views
10K
Roational Mechanics of Helicopter Blades
Replies
4
Views
9K
How do wind turbines do their thing?
Replies
9
Views
2K
Calculate Moment of Inertia & Angular Momentum of Helicopter Main Rotor
Replies
6
Views
2K
How Does Wind Turbine Blade Length Affect Power Output?
Replies
2
Views
2K
Helicopter air projection velocity problem
Replies
8
Views
3K
Vertical wind turbine with two concentric rotors
Replies
7
Views
3K

Hot Threads

Recent Insights

Back
Top