Physics question?

Question

Strange as it may seem, if a rifle is fired horizontally and a bullet is dropped at the same time, they hit the ground at the same time. This is because all things fall at the same rate, no matter how fast it may go horizontally. See if you can verify this phenomenon or diprove it.
Why?

Answer 1

The bullet has both horizontal and vertical motion, but only the vertical motion is affected by gravity. As far as gravity is concerned, the fired bullet and the dropped bullet are identical, because gravity cannot effect the horizontal motion -- only air resistance can. A bullet is falling from the moment it leaves the gun, so if a bullet is fired and another bullet is dropped from the same height, gravity pulls both down at the same rate, and both hit the ground at the same time. The fired bullet travels a lot farther horizontally, but both travel the same distance vertically.

All this is, of course, barring air resistance, which could influence the vertical motion as well as the horizontal.

Does that help?

JIM

Answer 2

The way my physics teacher proved this was as follows:

He set up a "blow gun" with a marble in a tube. He then had a metal can attached to a electro-magnet on the ceiling. There was a switch at the end of the "blow gun" that would turn off the electro-magnet. The "blow gun" was aligned in a straight line with the can.

Now when the marble is propelled out of the gun with some initial velocity, it starts the can falling. It accelerates downward with gravity. Sure enough, the bullet would also fall with the same vertical acceleration. You could tell because you'd hear a big "ping" as the bullet hit the can.

Any other aiming (above or below the can) would miss. And the initial velocity didn't matter. Several attempts at different blowing strengths still hit the can, thus proving that the horizontal component of the bullet's motion had no effect on its vertical component.

Answer 3

The rate the bullet travels vertically is just the 9.8 ms^-2 so the vertical force is this acceleration *the mass , there are no other vertical forces acting on it.
The explosion in the gun only acts on it horizontally.

Draw a free body force diagram and it will become very obvious.

However there may be some effects due to fluid dynamics, as it is travellinng very fast and depending on its shape may produce lift?
Probably cancelled out by the fact it is spinning though (due to rifiling).

Answer 4

Again you are in error. There is a certain velocity, above which the bullet will either orbit or leave the Earth. Even below that velocity the bullet could spiral inward toward the Earth and land 24000 miles away (behind the gun). Your statement is only true for slow bullets.

Answer 5

is the second bullet dropped from the same place the first bullet was shot? I mean same height above ground?

If so, then you already proved it. The rifle provides the x-direction force, and gravity provides for the y-direction force. The y-direction force is gravity and it's the same for both bullets, so they hit the ground at the same time.

Answer 6

this only works if you assume that the earth is perfectly flat. you dont need to do any maths to see that in the extreme case that the earth was say, as small and round as a beachball any bullet you fired tangent to the curved surface would never touch ground and fly off into space. in reality of course the actual extra distance downward the bullet has to fall because the ground is curving away underneath it will be fairly small!

Answer 7

the bullet fired from the rifle has force behind it. to things will fall at the same speed only if they have the same force behind them. try dropping to of the same thing at the same time. just let go with one hand and flick the object out with the other. see witch hits first.

Answer 8

It has to do with the vector nature of Newton's equations. The gravitational force is acting at right angles to the horizontal.

Answer 9

I know that all things that fall will fall at the same rate but the horizontal bullet thing doesn't make sense.

Answer 10

What drugs are you on, man? This is basic high school physics. Do you see yourself as some sort of super physics teacher, setting questions with "hints" for poor mortals who know less than you? Have you got any real original interesting questions instead of these contrived boring ones?