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allochka39001 [22]
3 years ago
12

An athlete with mass m running at speed v grabs a light rope that hangs from a ceiling of height h and swings to a maximum heigh

t of 1 h . in another room with a lower ceiling of height 2 h , a second athlete with mass 2m running at the same speed v grabs a light rope hanging from the ceiling and swings to a maximum height of 2 h . how does the maximum height reached by the two athletes compare, and why?

Physics
1 answer:
Agata [3.3K]3 years ago
8 0
The image shows the original problem. Let me know if this is this is the answer to the problem that you wanted:

Remember that the mechanical energy E_m=E_k+E_p of the system, (where E_k, E_p are the kinetic energy and the potential energy respectively) must remain the same. In an initial situation, the athletes have purely kinetic energy. Then they hang on to the rope and reach a maximum height, at which point they have zero speed and thus zero kinetic energy. The athletes now have purely potential energy, remember again that the mechanical energy must be the same than it was initially, this implies that:
E_k=E_p\implies\frac{1}{2}mv^2=mgh_1\implies h_1=\frac{V^2}{2g}
For the first athlete, and
E_k=E_p\implies\frac{1}{2}(2m)v^2=mgh_2\implies h_2=\frac{V^2}{g}
for the second athlete.
We can see clearly that the second athlete rose higher than the first athlete.


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Nonamiya [84]

\\ \bull\tt\longrightarrow P=\dfrac{V^2}{R}

  • P is power
  • R is resistance

\\ \bull\tt\longrightarrow R=\dfrac{V^2}{P}

Hence

\\ \bull\tt\longrightarrow R\propto V

\\ \bull\tt\longrightarrow R\propto \dfrac{1}{P}

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The first bulb has less power hence it has greater filament resistance.

5 0
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How do I do this physics problem about potential energy and kinetic energy?
larisa86 [58]

Ok i apologise for the messy working but I'll try and explain my attempt at logic

Also note i ignore any air resistance for this.

First i wrote the two equations I'd most likely need for this situation, the kinetic energy equation and the potential energy equation.

Because the energy right at the top of the swing motion is equal to the energy right in the "bottom" of the swing's motion (due to conservation of energy), i made the kinetic energy equal to the potential energy as indicated by Ek = Ep.

I also noted the "initial" and "final" height of the swing with hi and hf respectively.

So initially looking at this i thought, what the heck, there's no mass. Then i figured that using the conservation of energy law i could take the mass value from the Ek equation and use it in the Ep equation. So what i did was take the Ek equation and rearranged it for m as you can hopefully see. Then i substituted the rearranged Ek equation into the Ep equation.

So then the equation reads something like Ep = (rearranged Ek equation for m) × g (which is -9.81) × change in height (hf - hi).

Then i simplify the equation a little. When i multiply both sides by v^2 i can clearly see that there is one E on each side (at that stage i don't need to clarify which type of energy it is because Ek = Ep so they're just the same anyway). So i just canceled them out and square rooted both sides.

The answer i got was that the max velocity would be 4.85m/s 3sf, assuming no losses (eg energy lost to friction).

I do hope I'm right and i suppose it's better than a blank piece of paper good luck my dude xx

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Answer: I think its 120

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