A model of a helicopter rotor has four blades, each 3.40 m long from the central shaft to the blade tip. The model is rotated in a wind tunnel at 550 rev/min. (a) What is the linear speed of the blade tip, in m/s? (b) What is the radial acceleration of the blade tip expressed as a multiple of g?

Respuesta :

Answer:

(a) [tex]v=31.16\frac{m}{s}[/tex]

(b) [tex]a_r=29.14g[/tex]

Explanation:

(a) The linear speed in a circular motion is defined as the distance traveled in one revolution divided into the time taken to complete one revolution. So, we have:

[tex]v=\frac{2\pi r}{T}[/tex]

Here r is the radius of the circular motion, that is, the distance from the central shaft to the blade tip. As can be seen this time is the period, which is defined as:

[tex]T=\frac{2\pi}{\omega}[/tex]

[tex]\omega[/tex] is the angular speed. Replacing this in the linear speed equation:

[tex]v=\frac{2\pi r}{\frac{2\pi}{\omega}}\\v=\omega r\\v=550\frac{rev}{min}(3.40m)\\v=1870\frac{m}{min}*\frac{1min}{60s}\\v=31.16\frac{m}{s}[/tex]

(b) The radial acceleration is given by:

[tex]a_r=\frac{v^2}{r}\\a_r=\frac{(31.16\frac{m}{s^2})^2}{3.40m}\\a_r=285.57\frac{m}{s^2}\\\\\frac{a_r}{g}=\frac{285.57\frac{m}{s^2}}{9.8\frac{m}{s^2}}\\\frac{a_r}{g}=29.14\\a_r=29.14g[/tex]

Answer: b.) (1.15 x 10^3)g

Explanation: