# PHYSICS HELP!

posted by .

A typical propeller of a turbine used to generate electricity from the wind consists of three blades as in the figure below. Each blade has a length of L = 33 m and a mass of m = 415 kg. The propeller rotates at the rate of 21 rev/min. 120degree angle between blades
a) Convert the angular speed of the propeller to units of rad/s.
(b) Find the moment of inertia of the propeller about the axis of rotation.___J ยท s2
(c) Find the total kinetic energy of the propeller.______ J

• PHYSICS HELP! -

This is pretty standard question. What is it you do not understand?

For the moment of inertial figure each blade rotating about its end, then multiply by three.

KE=1/2 Itotal*w^2

• PHYSICS HELP! -

(A) w = (21rev/min) * (1min/60sec) * (2pi rad/1rev) = 2.2 rad/s

(B)

I = MR^2
I = (415kg)(33m)^2
I = 4.52E5 (I for one propeller)

I for all three propellers = (4.52E5) * 3 = 1.36E6

(C) KE = (1/2) * Iw^2

= (1/2)(4.52E5)(2.2)^2
=1.1E6 J

The book gives solutions for I and KE using one propeller. My thought were to multiply I *3....a little confusing. Thoughts...?

## Similar Questions

1. ### physical

Part A Each blade on a wind turbine is engineered to produce an effective force through its center of mass that is perpendicular to its long axis. (Part A figure) The magnitude of the force produced by each blade in a wind of speed …
2. ### College Physics

In Chapter 3 we learned that the force of air drag on an object moving rapidly through the air is proportional to v2, where v is the speed of the ball relative to the air. The same relation applies to the force of the wind on the blades …
3. ### Physics

1. A model of a helicopter rotor has four blades, each 2.50 m in length from the central shaft to the blade tip and is rotated in a wind tunnel at 1800 rev/min, a. what is the linear speed of the blade tip in m/s?
4. ### Physics

Each of the space shuttle's main engines is fed liquid hydrogen by a high-pressure pump. Turbine blades inside the pump rotate at 595 rev/s. A point on one of the blades traces out a circle with a radius of 0.02 m as the blade rotates. …
5. ### algebra

Wind farms are a source of renewable energy found around the world. The power P(in kilowatts) generated by a wind turbine varies directly as the cube of the wind speed v(in meters per second) If a turbine generates 700kW in a 5m.s …
6. ### PHYSICS

In a power plant the high pressure turbine trips due to an unauthorised valve shutdown. What are a) what is the angular acceleration of the turbine blade?
7. ### PHYSICS

In a power plant the high pressure turbine trips due to an unauthorised valve shutdown. What are a) what is the angular acceleration of the turbine blade?
8. ### PHYSICS

In a power plant the high pressure turbine trips due to an unauthorised valve shutdown. What are a) what is the angular acceleration of the turbine blade?
9. ### trigonometry

a wind mill is used to generate electricity. the wind mill has propeller blades that are 12 feet in length. if the propeller is rotating at 3 revolutions per second, what is the linear speed in feet per seconds of the tips of the blades?
10. ### Algebra, Trig

Question: A wind turbine has a total height of 50m, with 3 equally spaced blades that are 16m in diameter. 1) Create equations modelling the height of points on the tips of blades One, Two and Three. Graph these three curves on one …

More Similar Questions