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If a plane is flying at a constant speed at some altitude like 5-6 km and it releases a bomb:

  • does the bomb move forward at the same horizontal speed as the airplane?
  • or does its horizontal speed decrease due to drag and no thrust to push it forward?
  • or does it outrun the airplane because it's more aerodynamic than the airplane and the gravity is adding to its horizontal speed?
  • or does it depend on the bomb? If so, what would be the typical scenario?

I looked at a demonstration on Wolfram Alpha (http://demonstrations.wolfram.com/TrajectoryOfABomb/ - requires a plugin) and it looks like the bomb moves forward at the exact same speed as the plane, and I don't know if that's accurate.

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In a completely ideal world, where air resistance was not present, the bomb would continue to move forward and the same horizontal speed as the airplane it was dropped from. Gravity only acts in the perpendicular direction, thus has no effect on the horizontal component of the bomb's velocity. In reality though, air friction reduced the speed of the bomb as time passes, as there is no force being applied to it.

I hope this answers your question.

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  • $\begingroup$ But how does gravity accelerate objects on a decline surface? Isn't the air that the bomb falls through kind of the same thing (but a lot less dense obviously)? $\endgroup$ – TimSim Jul 4 '14 at 18:50
  • $\begingroup$ @TimSim It is the surface reaction (normal force) that causes the horizontal component of that acceleration. $\endgroup$ – dmckee Jul 4 '14 at 18:53
  • $\begingroup$ So is that surface reaction present when a bomb moves through the air? My question is if it's only the air drag that slows down the bomb or is there something that pushes it forward (like the way gliders fly). $\endgroup$ – TimSim Jul 4 '14 at 18:56
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    $\begingroup$ @TimSim Nothing pushes gliders forward, they move forward due to their initial velocity, and due to their ability to take advantage of air currents and air drag. Likewise, nothing pushes a dropped bomb forward. The surface reaction present in case of a inclined plane is due to the solidity of the wedge, which cancels out the force exerted by gravity perpendicular to the surface. This is not present in our case, as there is no solid surface in the case of the bomb. $\endgroup$ – Gummy bears Jul 4 '14 at 19:01

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