Please help?

Question

Tarzan (m = 85 kg) tries to cross a river by swinging from a 10-m-long vine. His speed at the bottom of the swing (as he just clears the water) is 8.0 m/s. Tarzan does not know that the vine has a breaking strength of 1000 N. Does he make it safely across the river? Justify your answer.

Answer 1

There are two parts, the gravitational force, and the centripital force

gravitational force is proportional to mass...

F = M* g

F = 85 * 9.8 m/s^2

F = 833... more or less.

Tarzan's MASS produces a pull of just over 833 newtons as I said in the PREVIOUS answer.

Now, we need to know the centripital force on a 10 meter vine where 85 kg has a velocity of 8 m/s.

F = m (V^2 / R )

F = 85 ( 8 * 8 / 10)

F = 85 *64/10

F = 544 newtons.

add THAT 544 to his 833 newtons he WEIGHS (See previous answer) and you get almost 1400 newtons.

But the breaking strength of the vine is 1000 N, so, it's swimming time.

Answer 2

This is a pendulum type question which requires you to calculate the centripetal force exerted on the vine

without going too crazy into formulas, as it has been over 10 years since I took college physics, I will tell you how to set up the problem to be solved

1. Find the centripetal force exerted on the vine

Fc=mv^2/r or 85kg*(8.0m/s)^2/10m=544N

The vine won't break because Tarzan only exerts 544 Newtons on the vine, not enough to exceed the vine's tensile strength of 1000N

I don't think Tarzan's weight (M*g) plays a big role in this equation, as the sole force here is centripital force, but I could be wrong
Tarzan is safe here

Answer 3

Im not positive but i think the first guy is right and the second guy is wrong. The reason is that if tarzan were just hanging from the vine without moving, his weight would exert a force of about 850N. But since Tarzan is swinging and accelerating, he is exerting a greater force on the vine which is why you add the centripital acceleration.