Kevin's Watch

Java™ Platform Standard Ed. 6 wrote:java.lang
Class String

length

public int length()

• Returns the length of this string. The length is equal to the number of Unicode code units in the string.
  
  Specified by:
  • length in interface CharSequence
  
  Returns:
  • the length of the sequence of characters represented by this object.

physicsforum.com wrote:1. The problem statement, all variables and given/known data
In this case how tights a peice of wire with a ball, at one end and a pivot P at the other. A wire from the pivot P suspends a ball, m.

Problem:Find T(r) for the values of m, v and g (in terms of r).



2. Relevant equations

The tension or force in the wire, T, when the ball m is swinging through the lowest point is given by the function:

T(r)=mg+(mv^2/r) where m=1.0 kg, v=7.75 ms–1, g = 9.81 ms-2 T is in Newtons

r is the disrance from the pivot P to the centre of the ball when the wire is stretched.When the wire is not stretched, its length is 2.89m.




3. The attempt at a solution

0=mg+(mv^2/r)
-mg=mv^2/r)
-mg(r)=mv^2
r=-mv^2/mg therefore r=-1x7.75^2/1x9.81 =-6.123m 3dp

Just wondering if Im on the right track here I dont see how r could be a negative number and if not how can it be twice the length when stretched?