Wenda+Xi


 * Fifth week (26th September, 2011) --- please consider this as a review for your exam too **

1. A light string of mass per unit length 8 g / m has its ends tied to two walls separated by a distance equal to three fourths the length L of the string. A mass m is suspended from the center of the string, applying a tension in the string. The acceleration of gravity is 9. 8 m / s². What size mass should be suspended from the string to produce a wave speed of 60 m / s?

i From the question, u is given 8g/m. V is given 60m/s. ii mg= 2Tsin(theta), T=(m*g)/2sin(theta) iii We find the formular for T, but we dont know theta, so find theta first. Cos(theta)=((3L)/4*1/2)/(L/2). iiii V=sqrt(T/u) V=sqrt( (m*g)/2sin(theta)/u)

iii pluge in what we have, so we can get mass.

2.A simple pendulum consists of a ball of mass M = 5 kg hanging from a uniform string of mass m = 0.6 g and unknown length L. The pendulum is located in gravitational field g = 9.8 m/s² and has period T = 2 s. Determine the speed of a transverse wave in the string when the pendulum is stationary and hangs vertically. (For simplicity, neglect the string’s weight compared to the ball’s weight. Likewise, neglect the ball’s radius compared to the string’s length). Answer in units of m/s