Physics Question

[rammstein]

I have recently become fascinated with physics. As in the last hour.

Here is the question:

10lb object in space moving at 10mph hits 5lb object moving Zerio Mph. The collision is dead on. What is the resulting speed of each object?

I know that the kinetic energy of the original object was 500 initially. But I don't know how much transfers to the stationary object.

Whats weird is that I have a known fact- if the object was to hit another object of equal weight, the original object would stop completely and the 2nd object would take on all of the original speed. Like in curling if you were to hit the other rock dead on, or those desktop thingies where you have 5 balls, drop one and the one on the other side goes up equally, then back and forth indefinitely (until friction with the air and the collision heat and sound eventually stops it)

Assume zero friction, meaning no loss of kinetic energy due to heat loss or sound waves.

[gassy]

Pi.

[Aerkuld]

Originally Posted by gassy

Pi.

Oh yes please. I missed lunch.

[kach22i]

Try asking in here:
http://www.physicsforums.com/

[Overpaid Slacker]

assuming a completely elastic collision (like steel ball striking steel ball, not steel ball striking marshmallow fluff) I think we're dealing with conservation of momentum.

p=mv, and in a closed system, it's a constant. unlike kinetic energy.

v_{1,f} = \left( \frac{m_1 - m_2}{m_1 + m_2} \right) v_{1,i} + \left( \frac{2 m_2}{m_1 + m_2} \right) v_{2,i} \,

v_{2,f} = \left( \frac{2 m_1}{m_1 + m_2} \right) v_{1,i} + \left( \frac{m_2 - m_1}{m_1 + m_2} \right) v_{2,i} \,

I don't think that's going to read very well, so check out here: http://en.wikipedia.org/wiki/Momentum

What's going to be the interest in the next hour?

JP

[dd74]

Originally Posted by rammstein

10lb object in space moving at 10mph hits 5lb object moving Zerio Mph. The collision is dead on. What is the resulting speed of each object?

0 mph for the 10-lb object: contingent on its insurance policy being canceled.

[rammstein]

Originally Posted by The Gaijin

I wish I was Newton.

The 10lb object would lose have its energy and move forward half as fast... 5MPH?

And the 5lb object gaining half that energy, but at half the weight would speed up to 10MPH??

Nope- I thought this at one point, but it fails like this:

Initial system Energy MUST EQUAL New System Energy

Initial system Energy = 500

In your new system, its (10)(5 squared) + (5)(10 squared) = 750

You've created energy.

[rammstein]

Originally Posted by Overpaid Slacker

assuming a completely elastic collision (like steel ball striking steel ball, not steel ball striking marshmallow fluff) I think we're dealing with conservation of momentum.

p=mv, and in a closed system, it's a constant. unlike kinetic energy.

v_{1,f} = \left( \frac{m_1 - m_2}{m_1 + m_2} \right) v_{1,i} + \left( \frac{2 m_2}{m_1 + m_2} \right) v_{2,i} \,

v_{2,f} = \left( \frac{2 m_1}{m_1 + m_2} \right) v_{1,i} + \left( \frac{m_2 - m_1}{m_1 + m_2} \right) v_{2,i} \,

I don't think that's going to read very well, so check out here: http://en.wikipedia.org/wiki/Momentum

What's going to be the interest in the next hour?

JP

I've been research elastic collisions... and yes, we are talking like two steel balls, no marshmellows. I am looking at the page you linked, and much like I always felt in school, its too much to take in- could you plug my numbers into a formula? Please? You know you want to show just how smart you are...

[The Gaijin]

That is the full formula..

The best cheat sheet I can figure:

With one object half as heavy as the other, the heavy object slows to 1/3 the orginal speed and the lighter one accelerates to 4 times that slower speed.

Try that out (rounding up or down a sukosh..) and see if it works..

[Bill Verburg]

Originally Posted by Overpaid Slacker

p=mv, and in a closed system, it's a constant. unlike kinetic energy.
JP

In a closed system, a 100% elastic collision conserves both momentum and kinetic energy

In a closed system, a 100% inelastic collision only conserves momentum.

[sketchers356]

This thread is hilarious.

CONSERVATION OF FOUR-MOMENTUM, USE IT!

[javadog]

Originally Posted by rammstein

10lb object in space moving at 10mph hits 5lb object moving Zerio Mph. The collision is dead on. What is the resulting speed of each object?

Smaller object now traveling at 20mph. Larger object not moving.

JR

[TheMentat]

that got me thinking... did you guys & gals in the US have to learn Physics using Imperial Units?

[masraum]

Originally Posted by TheMentat

that got me thinking... did you guys & gals in the US have to learn Physics using Imperial Units?

I learned kilograms, m/s, f/s, slugs (the mass version of pounds which is force, not mass), pounds, Newtons, etc... I couldn't tell you diddley about "stones", but I've got what the US calls Standard/English and metric down.

Most of our word problems and work was done in metric units.

[sjf911]

IIRC, it should be 1/3 of V1 for M1 and 4/3 of V1 for M2. So 3.3333mph and 13.3333mph.

[vash]

i refuse to look it up, but that exact problem (diff masses i am sure) is in my dynamics textbook. it is rather simple, from what i remember. which is almost zero. heheh.

[Dantilla]

Does the 10-pound object have a "Type R" sticker on it? If so, you can't ignore it's massive torque.

[artplumber]

Pool. Lots of Pool. Then add spin......

[slodave]

Sometimes, the hardest questions are best answered while on the crapper.

[kstar]

After the collision, the 5lb object will be moving at the speed of 4 Libraries of Congress.