This is a classic Physics question that shows up in many forms on high school physics exams. The question goes as follows: A gun is aimed at a monkey sitting in a tree. Exactly as the trigger is pulled, the monkey drops from the tree. Ignoring air resistance, where should you aim the gun so as to hit the monkey?
Know the answer? It’s “right where he was sitting.”
The reason is that gravity is working on both the bullet and monkey equally. If there were no gravity, then the bullet would travel in a straight line and the monkey would not fall anywhere. Add gravity, which causes downward acceleration at a rate of 32 ft/sec/sec, both the bullet and the monkey fall at the same rate.
Sounds illogical, but that’s the way the world works. Of course, if the monkey shaped his body differently as he fell, he would increase or decrease his wind resistance, thus changing the answer. Visit Everything2.com for more discussion of why this is so.
When I was in Physics class in high school, my teacher had a little metal contraption that was mostly a spring and a rod. There were two balls that both had holes drilled through the center. When you pulled the rod back against the spring and latched it, thus “cocking” the machine like a gun, one ball was put onto the back end of the rod and the other was placed in front of the rod. When you “unlatched” it, the rod shot forward, knocking the front ball straight forward while pulling out of the back ball, allowing it to drop. On a classroom countertop over a hard floor, it was easy to hear that both balls hit the ground at exactly the same time.
Go figure!
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July 27th, 2006 at 9:35
Wrong, the gun should be sighted to take into account the gravitational pull on the bullet. In order to answer the question with a sighted gun you would need to know the distance from the monkey.
(yeah, I know, I’m splitting hairs, but I couldn’t resist.)
July 27th, 2006 at 11:32
Okay, the physics works as long as you don\’t have a sight on your rifle.
Just point and shoot.
August 10th, 2006 at 20:04
Hey Scott,
I’m gonna have to call “bullshit” on the story about “…my teacher (having) a little metal contraption…”
I don’t recall Mrs. Blondeau having any such thing. And we had the same class, my friend.
‘85 is alive! SMHS
Beans
August 11th, 2006 at 10:06
Well, I don’t know who Beans is, but I’m glad to hear from somebody that was is Mrs. Blondeau’s class.
I was also her “teacher’s aide” for her AP Physics class the following year.
And she most definitely DID have this little contraption. Used to set it on the corner of her lab desk so one ball would drop to the floor while the other shot out. The gadget and the balls all were metal and silver.
It worked kind of like this: http://demo.physics.uiuc.edu/LectDemo/scripts/demo_descript.idc?DemoID=83 or http://www.physics.umd.edu/deptinfo/facilities/lecdem/services/demos/demosc2/c2-21a.mpg
but it was shorter and all silver.
Here’s another website that illustrates it (look under Simultaneous Fall): http://www.physics.umn.edu/outreach/pforce/projectile.html