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/sci/ - Science & Math

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1080239 No.1080239 [Reply] [Original]

Hey guys. I had a physics test today, and it went great but there was just this one question that puzzled me.
A ball thrown into the air at a velocity of 16 m/s has a velocity of 14.8 m/s at the same point when it comes down again. Did it loose more mechanical energy heading up or down?
Can anyone explain this to me?

>> No.1080272

Why do people consistently misspell the word "lose", as in "to lose (an object)? It's fucking lose! not loose! Loose refers to the opposite of tight! Jesus fucking Christ. Also, It lost kinetic engergy on it's way up, but gained potential energy until it reached the apex, at which point, it's potential energy begins to be converted to kinetic by the force of gravity acting on it.

>> No.1080273

I would guess heading up. The only thing it can lose mechanical energy to is drag, and drag is strongest and the highest speed. So when it first goes up it looses energy to drag, so it doesn't have as much speed going down so it looses less energy.

>> No.1080278

>>1080272
loose up man

>> No.1080282
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1080282

>>1080273
>looses energy
>looses less energy

Seriously?

>> No.1080289

The potential energy stays the same, the ball loses more kinetic energy going up since the difference in velocity is greater than when going down, so more mechanical energy is lost going up.

>> No.1080291

>>1080278
aside from misspelling "loosen". Your shitty troll attempt is actually the correct usage of the word, shitdick.

>> No.1080295
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1080295

>>1080273
I knew it. Physics is just geussing

>> No.1080322

You guys do have a point when saying up, but (apart from wind resistance) does it lose energy at all going up? Is the kinetic energy not just transformed into potential energy?

>> No.1080328

>>1080273
I'm gonna reword this:
Drag basically takes off a percentage of the ball's mechanical energy. Lets say 5%.
Going up the ball goes down to 95% of its initial energy.
Then on the way back down drag takes off 5% of the ball's energy again. Only this time it was 5% of 95 rather than 5% of 100, so the ball lost more energy going up.

>> No.1080336

>>1080322
If we're talking about conservative forces yes, but then the ball would have exactly the same speed going down.

>> No.1080359

>>1080322
That's why I say wind resistance. What else could the ball lose energy to? Otherwise its just transferring mechanical to potential and back again.

>> No.1080442

I would say up because the force of drag depends on the velocity and you have a greater max velocity going up, so since it is the same distance the work should be greater.