# light arrow, medium arrow and heavy arrow, same speed=same trajectory??

9002 Views 71 Replies 44 Participants Last post by  ukxbow
this is for conversation sake only...been thinkin of this for the past few days and curious to know what ya'll think...suppose you got 3 arrows, 350 grains, 450 grains and 550 grains...no science behind the weights just random. if you could get all of them to fly at 300 fps, assuming you could tune each setup with bow poundage draw length whatever it took to get each one to shoot 300 fps would they all have about the same trajectory or would they heavier arrow drop off sooner..typically the heavier arrow is slower out of the same bow so it doesnt fly as flat but if you could get them all to shoot that fast...what do ya think??? same trajectory or not?:darkbeer:
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#### bow_hunter44

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No, not the same trajectory. Given the same velocity, the heavy arrow will fly the farthest! This is due to inertia, once moving a heavy object will resist its change in motion more than a light one.

#### robbbinhoodx

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everything on earth falls at the same rate of speed no matter what it weighs! a 10oz ball falls to the ground at exactly the same rate of speed as a ball that weighs 400 lbs so the answer to the question is yes they will all have the same tradjectory!

#### joehunter8301

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good answers so far...one yes and one no lol this could be a good debate...

#### DocMort

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The heavier arrow will be flatter at a further distance, Try it out just get an IBO arrow and then get an old aluminum shoot them at 90 yards going the same speed.

As far as the no, yes every does for arguements sake fall at the same rate of speed but your also talking about a horizontal force being applied.

#### SlimTastic

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Quick google search turned up this calculator > http://www.outdoorsden.com/archery/archbal.asp

I put in the numbers for 350, 450, and 550 grain arrows at 300fps from a 70lb bow zeroed at 20yds...same trajectory numbers for all three. I have no idea if this correlates to real world conditions, but I found it interesting.

#### Narf

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in a vacuum yes. The trajectory would depend on several things here on earth. A vanes angle, material, and size would change the drag on the arrow. The tip and diameter of the shaft would affect this also. So the answer I would give is no.

#### bow_hunter44

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Gravity accelerates everything at the same rate, everything does not fall at the same speed. So, two objects with roughly the same surface area dropped from the same height at the same time will hit the ground at the same time. Two bullets, one dropped, one shot from a gun - at the same time, at the same height will hit the ground at the same time. On the other hand, two bullets fired at the same velocity, from the same height - one heavy, one light, the heavy bullet will travel the farthest. The same argument holds true with arrows as well.

From a different perspective, consider a freight train and a pickup truck traveling at the same velocity and then have the power cut off, and then roll to a stop (assume the same coefficient of friction between the tires/wheels and the road/rail road track), which one will take the longest to stop? Obviously the freight train will take the longest time to come to a stop, due to its inertia. The same is true for arrows traveling with the same velocity, the heaviest arrow will travel the farthest (be the most difficult to stop) due to its inertia.

#### robbbinhoodx

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Gravity accelerates everything at the same rate, everything does not fall at the same speed. So, two objects with roughly the same surface area dropped from the same height at the same time will hit the ground at the same time. Two bullets, one dropped, one shot from a gun - at the same time, at the same height will hit the ground at the same time. On the other hand, two bullets fired at the same velocity, from the same height - one heavy, one light, the heavy bullet will travel the farthest. The same argument holds true with arrows as well.

From a different perspective, consider a freight train and a pickup truck traveling at the same velocity and then have the power cut off, and then roll to a stop (assume the same coefficient of friction between the tires/wheels and the road/rail road track), which one will take the longest to stop? Obviously the freight train will take the longest time to come to a stop, due to its inertia. The same is true for arrows traveling with the same velocity, the heaviest arrow will travel the farthest (be the most difficult to stop) due to its inertia.
i hear what you are saying......but tradjectory is determined by the gravitational pull on an object, and inertia is measured by the force it takes to stop an object! all things being equal as far as resistance and arrow dynamics, the heavy arrow will hit the ground at the same time. now if you put a parachute on the back end of the arrow the heavier arrow will go farther but that's another thread.

#### bow_hunter44

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i hear what you are saying......but tradjectory is determined by the gravitational pull on an object, and inertia is measured by the force it takes to stop an object! all things being equal as far as resistance and arrow dynamics, the heavy arrow will hit the ground at the same time. now if you put a parachute on the back end of the arrow the heavier arrow will go farther but that's another thread.
Exactly. From a simplistic view of the argument of the flight of a projectile, the only forces acting on the object are air resistance and gravity. The inertia of the heavy arrow will cause it to resist its change motion the most and fly the farthest.

#### joehunter8301

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good answers so far....i love hearing what everyone has to say. this could be an interesting topic...i guess i could be more specific. a 350 grain arrow leaving the bow at 300 fps and a 550 grain arrow leavin the bow at the same speed...at 60 yards will the both drop the same amount from line of travel or will the heavier arrow drop more from highest point of arch..make sense?

· Socket Man
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Just do it for real, take the three arrows and with a chrono back your bow off until your arrow shoots 280 for each arrow and then go out into a field and see which arrow shoots the farthest. Pick something on the horizon to aim at and use it for each arrow. Make sure to use the same fletching for each arrow preferably straight fletch blazers to cut down on drag differences.

#### reylamb

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this is for conversation sake only...been thinkin of this for the past few days and curious to know what ya'll think...suppose you got 3 arrows, 350 grains, 450 grains and 550 grains...no science behind the weights just random. if you could get all of them to fly at 300 fps, assuming you could tune each setup with bow poundage draw length whatever it took to get each one to shoot 300 fps would they all have about the same trajectory or would they heavier arrow drop off sooner..typically the heavier arrow is slower out of the same bow so it doesnt fly as flat but if you could get them all to shoot that fast...what do ya think??? same trajectory or not?:darkbeer:
Maybe, are all other factors equal? Same diameter, same arrow composition, same arrow spine, same fletching type?

everything on earth falls at the same rate of speed no matter what it weighs! a 10oz ball falls to the ground at exactly the same rate of speed as a ball that weighs 400 lbs so the answer to the question is yes they will all have the same tradjectory!
Everything falls at the same rate in a vaccuum......drop a feather and drop a bowling ball from the same height and let me know which one hits the ground first..as long as you do not drop it is a vaccuum the bowling ball will hit the ground first....

#### TailChaser

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They fall at the same rate. If they are the same speed all the way to the target, and the FOC is the same, they will fall the same. The heavier arrow allows you to use bigger vanes since it is harder to slow down, and it needs bigger vanes to stabilize it the same.

#### DocMort

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They fall at the same rate. If they are the same speed all the way to the target, and the FOC is the same, they will fall the same. The heavier arrow allows you to use bigger vanes since it is harder to slow down, and it needs bigger vanes to stabilize it the same.
Not true, The heavier arrow has more mass therefore it takes more force to change direction in simple terms try it we did.

#### nuts&bolts

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everything on earth falls at the same rate of speed no matter what it weighs! a 10oz ball falls to the ground at exactly the same rate of speed as a ball that weighs 400 lbs so the answer to the question is yes they will all have the same tradjectory!
ONLY in a vacuum.

When you factor in aerodynamics,
and you take into account friction from moving through the air...(skin friction)
and you take into account aerodynamic lift and center of pressure for lift...
and you take into account FOC...

then,
the trajectory will be slightly different.

#### nuts&bolts

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good answers so far....i love hearing what everyone has to say. this could be an interesting topic...i guess i could be more specific. a 350 grain arrow leaving the bow at 300 fps and a 550 grain arrow leavin the bow at the same speed...at 60 yards will the both drop the same amount from line of travel or will the heavier arrow drop more from highest point of arch..make sense?
Need to know the FOC to answer this question.

#### C Doyle 88

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in a vacuum yes. The trajectory would depend on several things here on earth. A vanes angle, material, and size would change the drag on the arrow. The tip and diameter of the shaft would affect this also. So the answer I would give is no.

The gravity only guys ---are living in a vacuumn---

Think of the atmosphere as a liquid--just not as thick as water---the light shaft hasn't got the inertia to overcome that resistance---doesn't store as much energy---
It takes longer to blead energy out of a heavier shaft

Cec

#### Demp223

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Given identical or very similar arow setup heavier will stay flatter.Aero dynamic drag is what is primary decelerant on lighter arrow. Less mass to maintain it's forward momentum over distance. Roll a ping pong ball and golf ball at a same speed into a 5 mph headwind and see which one rolls farther. In vacuum test on earth you still have gravity,thus object fall at same rate due to lack of aerodynamic drag. Cold damp days arrow will travel shorter. Hot dry days longer. Mind you we are talking a few inches difference at 100 yds but that could be all the difference between first and first loser.

#### CoppertoneSPF15

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i hear what you are saying......but tradjectory is determined by the gravitational pull on an object, and inertia is measured by the force it takes to stop an object! all things being equal as far as resistance and arrow dynamics, the heavy arrow will hit the ground at the same time. now if you put a parachute on the back end of the arrow the heavier arrow will go farther but that's another thread.
Drag IS your "parachute". Assuming similar fletching size, shaft diameter, etc... drag will decelerate the light arrow the quickest and the heavy arrow the slowest.

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