# Homework Help: Mass of a String

1. Jan 19, 2010

### Samurai Weck

1. The problem statement, all variables and given/known data
A 1.50-m-long string is under 30.0 N of tension. A pulse travels the length of the string in 50.0 ms.

2. Relevant equations

v of string = sq rt of (Tension of string/ string's mass-to-length ratio)

string's mass to length ratio= m/L

3. The attempt at a solution

So, the pulse takes 50.0 ms to travel through 1.5 m of string. So, the velocity of the pulse is 1.5 m/.050 s.

V= 1.5/.050 = 30 m/s

Now that I know the velocity, I can use the V of string equation.

V$$^{2}$$= T/$$\mu$$
$$\mu$$= T/V$$^{2}$$
$$\mu$$= 30.0N/ (30m/s)$$^{2}$$
$$\mu$$=.033

$$\mu$$=m/L
$$\mu$$*L=m
.033*1.5=m
m=.049995 or .05 g

However, master physics disagrees with this answer. What am I doing incorrectly?

Last edited: Jan 19, 2010
2. Jan 19, 2010

### kuruman

The answer should be in kilograms not grams.

3. Jan 19, 2010

### Samurai Weck

Actually, the unit they want mass in is g. Sorry. Forgot to put that in there.

4. Jan 19, 2010

### kuruman

I was not clear explaining what I meant. The answer that you got, 0.05 is in kilograms. You need to convert that to grams. Did you enter 0.05?