Tension in vine as Tarzan swings past intercepting branch

[R_H_A]

Homework Statement

Tarzan (mass of 80kg) has an 18m vine stretched horizontally from his hut to a pivot point P, as shown. He uses it to swing across the gorge to visit Jane's hut, starting from rest to conserve energy. One day Jane spoiled his plans by fastening a strong, thin, smooth, horizontal branch to intercept the vine at B, 15m directly below P. Tarzan hung on and followed the dotted path 1 to 2 to 3. Calculate the tension in the vine as he passed through point 3. How many times greater than his weight is his tension?

The answer is 15.34 (I'm unsure which question this answers)

Homework Equations

Ug =mgh
ΣE = 0
Ek = 0.5mv²
ΣF = ma

The Attempt at a Solution

1: [/B]Ug = 80(9.81)(18)= 14,126.4 J
Ek = 0.5mv² = 0

2: Ug = 0
Ek = 0.5mv²
14 126.4= 0.5mv²
v = 18.795 m/s

Ft = mg = 784.8 N

 

[saarika]

it answers the tension in the vine as he passed through point 3. because if it would be the weight then the units would have been mentioned.

 

[haruspex]

In your step 2 you calculate a velocity. At what point is that his velocity? At which point do you need to determine his velocity?
As I'm sure you know, F_net=ma. If the tension at point 3 is T, what is F_net? What is his acceleration at that point?