# Homework Help: More on fundamental frequency

1. Jan 6, 2005

### Soaring Crane

A horizontal string of length 1.5 m vibrates with a wave velocity of 1320 m/s at its fundamental freq.

a. What is the fund. freq.?

Do I use the formula f_1 = v/4L?

b. What is the freq. of the 4th overtone and how many nodes and antinodes will it have?

To find 4th's freq. use f_n = 4*f_1?

Since this is 4th overtone, are there 6 nodes and 5 antinodes?

(assuming for 4th 5 positive crests on basic diagram for all situations)

c. In terms of interference to what do the nodes and antinodes correspond?

this is conceptual, right?

nodes - locations where string appears motionless due to destructive interference

antinodes - where string has greatest displacement due to constructive displacement.

d. how many g must string be to have a tension of 10^5 N?

Just use v = sqrt[F/(m/L)]

2. Jan 6, 2005

### Staff: Mentor

No. The general formula is $f_m = m v/2L$.

The 4th overtone is the 5th harmonic (m = 5 in the above formula).
Just by accident, this is correct.

Right (but that's constructive interference).

Right.