[teacake (OP)]

Would a planet's gravitational pull affect the speed with which a comet approaches a planet, and its impact on that planet?  And would an atmosphere slow or break up the comet at all, reducing its impact?  We are debating whether a comet would have more impact on Jupiter or Earth (knowing of course that Jupiter is all gas).

[vdurbha]

IMHO, the speed with which any body moves is the result of net force acting on that body. So in the case of a comet, it's velocity will be definitely determined by all forces (including gravitational forces) acting on it. So certainly, the gravitational force of the planet towards which it's approaching will be the dominant force on the comet and it will certainly will have a major influence on how much speed it will approach it. I also should mention that it also depends largely on it's velocity before it reaches the influence of gravity of the approaching planet.

Since Jupiter is much larger than earth (gravity is approximately 2.4 times of earth), I would think that the comet would be attracted by Jupiter with a much greater force and hence it would fall into Jupiter with a higher velocity when compared to earth.

Whether the comet will burn in the atmosphere of a planet, or hit the planet's ground, largely depends on the density and the composition of the atmosphere of that planet. The higher the density, the larger the frictional forces acting on the comet and hence more likely that it will burn out in the atmosphere.

I don't really know how Earth and Jupiter differ in their atmospheres.

[teacake (OP)]

Thank you!  That makes sense.

[Soul Surfer]

The earth's gravity if acting alone would cause a comet impact to be pretty nasty but as most comets come in from the outer regions of the solar system the sun's gravity has much more effect on the speed of comets hitting both the Earth and Jupiter.  Coming through the earth's atmosphere will vapourise a few millimeteres of surface material on any object coming into the atmosphere at high speed.  This would be pretty spectacular but not do much to protect us from any sizable object.

[jolly]

hi first time in how does this work??

[jolly]

its alright i think i get it.

[jolly]

deleted as inapproprate

[jolly]

noones here so i'll move on.