Help Solve Energy Problem 2: Tarzan & Jane's Swing

  • Thread starter Thread starter Port
  • Start date Start date
  • Tags Tags
    Energy
AI Thread Summary
Tarzan and Jane, with a combined mass of 130kg, start swinging from a 5m vine at a 30-degree angle. To find the maximum height Tarzan can reach after Jane releases the vine, one can calculate the change in potential energy as they swing down. The initial height can be determined using the formula r - r cos(θ), leading to the potential energy at the bottom of the swing being converted into kinetic energy. This kinetic energy can then be used to find the maximum height Tarzan can achieve after Jane lets go. Ultimately, it is suggested that Tarzan could reach the same height as the initial swing position.
Port
Messages
28
Reaction score
0
i kinda also need help on another problem. i can't even start this problem because i have no idea how! can someone please tell me how?

Tarzan and Jane, whose total mass is 130kg, start their swing on a 5m long vine when the vine is at an angle of 30 degrees with the horizontal. At the bottom of the arc, Jane, whose mass is 50kg, releases the vine . What is the max height at which Tarzan can land on a branch after his swing continues?
 
Physics news on Phys.org
ok so its 30 degrees from the horizanrtal and the rope is 5m long so you can fidn the diference from their current height and the height at the bottom of the arc right? with that height you can use the potential energy forumla mgh(mass x gravity x height). And I think, not totally sure, you can set that equal to the potential energy at the max height reached which would be mass of just tarzan x gravity x max height. solve for max height
 
In order to be able to do this, you need to assume some initial speed- probably you are to assume that Tarzan and Jane just grab the vine and drop so the initial speed is 0. You know the initial height compared to the height at the bottom of the arc- it's
r- r cos(θ)= r(1- cos(30))= r\frac{2-\sqrt{3}}{2}- so you can calculate the change in potential energy= kinetic energy and so the velocity at the bottom of the arc. Tarzan now has that velocity so you can calculate his kinetic energy and convert that to potential energy to find the maximum height.

HOWEVER, I believe that the two persons could be treated separately anyway- I can see no reason why Tarzan would not rise up to the same height as initially.
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top