Calculating Tarzan's Speed on a Swing: Solving for Velocity in a Physics Problem

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Tarzan's swing problem involves calculating his speed at the bottom of a 34 m vine swing, starting from rest and with an initial push of 4 m/s. The key equations discussed include work-energy principles and conservation of energy, which incorporate potential energy without needing mass for the calculations. The student expresses confusion about how to proceed without mass values, but others suggest focusing on energy conservation to solve the problem. The conversation highlights the importance of understanding energy concepts in physics problems. Overall, the discussion emphasizes the application of energy conservation in determining speeds in swing dynamics.
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Homework Statement


Tarzan swings on a 34 m long vine initially inclined at an angle of 41 degrees with the vertical.
The acceleration of gravity is 9.81 m/s^2.
What is his speed at the bottom of the swing if he starts from rest?
What is his speed if he pushes off with a speed of 4 m/s?


Homework Equations


w=(f)(d)(cos theta)
w= KEF - KEI

The Attempt at a Solution


I got the work, but how can you possibly find out his speed if a mass is not given? I'm thinking that it might have something to do with the kinetic energy equation, but you need mass for that. I'm not really sure of what to do now. I have a similar question like this, but with a loop-the-loop, which also does not give a mass. Someone please help!
 
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Please help, I am really lost.
 
Maybe someone can help me with a more difficult problem if no one is going to answer anything from above.

A student performs a ballistic pendulum experiment using an apparatus similar to that shown in the figure.
Initially the bullet is fired at the block while the block is at rest (at its lowest swing point). After the bullet hits the block, the block rises to its highest position (3 cm), and continues swinging back and forth.
max height : 3 cm
max height subtend angle: 36.9 degrees
mass of bullet : 99 g
mass of pendulum bob: 825 g
accel of gravity: 9.8 m/s^2

Detrmine the initial speed of the projectile. Answer in units of m/s.
 
bikerkid said:

Homework Statement


Tarzan swings on a 34 m long vine initially inclined at an angle of 41 degrees with the vertical.
The acceleration of gravity is 9.81 m/s^2.
What is his speed at the bottom of the swing if he starts from rest?
What is his speed if he pushes off with a speed of 4 m/s?


Homework Equations


w=(f)(d)(cos theta)
w= KEF - KEI

The Attempt at a Solution


I got the work, but how can you possibly find out his speed if a mass is not given? I'm thinking that it might have something to do with the kinetic energy equation, but you need mass for that. I'm not really sure of what to do now. I have a similar question like this, but with a loop-the-loop, which also does not give a mass. Someone please help!
You should instead be looking at the conservation of energy equation (which will include a potential energy term).
 
PhanthomJay said:
You should instead be looking at the conservation of energy equation (which will include a potential energy term).
I know the equation, but I don't understand where you are going with it.
 
Forget it, my peers figured out the equations necessary for the problems I could not answer while I was at work. Thanks anyway.
 
Thread 'Variable mass system : water sprayed into a moving container'

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}...
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