Centripetal force with circular motion

[catch-22]

This problem seems simple, but I can't get the answer:

Homework Statement

Tarzan tries to cross a river by swinging from one bank to the other on a vine that is 10.0 m long. His speed at the bottom of the swing is 8.0 m/s. Tarzan does not know that the vine has a breaking strength of 1000 N. What is the largest mass that Tarzan can have and still make it safely across the river.

Homework Equations

F_c=(m*v²)/(r)

The Attempt at a Solution

1000 N=(m*(8 m/s)²)/(10 m)
The answer is apparently 62 kg, and what I'm getting is over double that, so I'm obviously doing something wrong. I'm really not sure what I'm missing.

 

[hage567]

This problem seems simple, but I can't get the answer:

Homework Statement

Tarzan tries to cross a river by swinging from one bank to the other on a vine that is 10.0 m long. His speed at the bottom of the swing is 8.0 m/s. Tarzan does not know that the vine has a breaking strength of 1000 N. What is the largest mass that Tarzan can have and still make it safely across the river.

Homework Equations

F_c=(m*v²)/(r)

The Attempt at a Solution

1000 N=(m*(8 m/s)²)/(10 m)



The answer is apparently 62 kg, and what I'm getting is over double that, so I'm obviously doing something wrong. I'm really not sure what I'm missing.

The 1000 N is not Fc. It is the breaking strength (so the maximum tension the vine can withstand). There are two forces to consider. You have neglected to take into account Tarzan's mass on the vine. Draw a diagram to see it.

 

[Epsillon]

Ft is not the only force in this example.


mv2/r = Fc
Fc= Ft-Fg

 

[catch-22]

Ft is not the only force in this example.


mv2/r = Fc
Fc= Ft-Fg

I'm still not getting the right answer.

Using this, I've come up with

m=[10m*(1000 N-9.81^m/_s2*kg)]/(8.0^m2/_s2), which keeps working out to around 154 kg, still way off. What am I missing here?

 

[catch-22]

Nevermind, I got it. Thanks guys.

 

[rahuld.exe]

maximum tension is the tension at the lowest point
and
tension at the lowest point = mv2/r + mg
works to around 61.72 by taking g = 9.8m/s