Mark asked in Science & MathematicsPhysics · 5 months ago

# Question about momentum...?

Momentum, or P, = mv. And it is a law that momentum always has to he conserved through collisions. Suppose theirs an asteroid with a mass of 10^6 kg travelling at a constant velocity of 1 m/s. It hits another object with a mass of 1 kg. The momentum would be 10^6 kilogram meters/sec. so for the 1 kg object to conserve that momentum, it would need to travel at a velocity of 10^6 meters per sec? Or 1000 km/sec? I cant see how that would be right.

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• goring
Lv 6
5 months ago

Without Power causing the motion a mass would have no momentum

In collision momentum is conserved if the collision is perfectly elastic. In non elastic collision there is a change of mass,time and energy and volume and velocity in the two interacting masses

• 5 months ago

That isn't what happens. The big asteroid does not stop after the collision. It keeps going at a slightly slower speed.

You must use conservation of energy equations in addition to conservation of momentum to calculate the final speed of each object.

• 5 months ago

Firstly you have overlooked the physics of relativity.

Secondly you have overlooked your knowledge of collisions.

You could have a source of energy in a collision. But not in this case.

As energy may be lost then the speed of the small mass relative to the asteroid after the collision will be NO MORE than the relative speed prior to the collision.

ie if they were approaching at speed v1 then after the collision they will be going apart with a relative speed of v where 0<=v<= v1

• Anonymous
5 months ago

assume 1 kg mass initially stationary

inelastic collision

10*6 * 1m/s = (1+10^6) * V

final asteroid velocity V = 1m/s * 10^6 / (1 + 10^6)

so pretty close to 1 m/s

perfectly elastic collision

10^6 * 1m/s = 10^6 * V + 1 * (1 + V)

final asteroid V = 1m/s * (10^6 - 1) / (1 + 10^6)

slightly less than inelastic case,

but still quite close to 1 m/s

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• Anonymous
5 months ago

You are assuming all of the asteroid's momentum is transferred to the 1kg mass.

But that's not what happens - the asteroid keeps moving, so only a small fraction of its orignal momentum is transfered to the 1kg mass.

(The exact fraction depends on how elastic/inelastic the collision is.)

• D g
Lv 7
5 months ago

No your one kg object only hs to get a velocity of ten^6 if the bigger object SLOWS to zero

sorry my numbers are not working

if you have a fly and its still and you hit it with your hand does the FLY stop your hand NO .. it only accepts part of the momentum of your hand and moves forward in the direction of the hand was going the hand keeps on going but at a slower speed ....

if you want another example the use a iron ball on a chain it gets dropped ad swings toward the wall.. and smashes through the wall it does not stop

so your assumption is that all the momentum will transfer to the small object is wrong

the only time momentum is transered fully when the object hit is equal or larger in size

• oubaas
Lv 7
5 months ago

You cant see?? Maybe you are shortsighted...how about wear a couple of glasses ?? ^_-

• alex
Lv 7
5 months ago

That's true

if

the velocity of the asteroid is zero after the collision

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