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First Order ODE question on a projectile...

i need help with understanding this question - esp the part given in bold:

"In Dallas on November 22, 1963, President Kennedy was assassinated by Lee
Harvey Oswald (if you do not believe any of the conspiracy theories). Oswald
fired a Mannlicher-Carcano rifle from approximately 90 metres away. The
sight on Oswald’s rifle was less than ideal; if the bullet travelled in a straight
line after leaving the rifle (at a velocity of roughly 700 m/s) then the sight
aimed about 10 cm too high at a target 90 metres away. How much would the drop in the trajectory due to gravity compensate for this? (The initial vertical
velocity is zero, and satisfies dv/dt = -g, while the horizontal velocity is constant if we neglect air resistance.)"

I know its a projectile question using the ODE and equations of motion but the "sight" part is confusing me - help please!!
Reply 1
Avatar for Zii
Zii
13
The sight is like the aimhole. Its where the gun was aiming.
Reply 2
Avatar for zrancis
zrancis
2
I did this question the other night, problem sheet 1?

It basically means the rifle shoots 10cm too high but you need to work out how much gravity will make it fall and if this is less than, equal to or more than the 10cm error. It's firing in a straight line.
Reply 3
Avatar for ramdayal
ramdayal
OP
1
i seem to get the drop due to gravity being 81g/9800 is this correct? - the thing is i dont really understand wat the question is askin for...
Reply 4
Avatar for zrancis
zrancis
2
Yep, take g=9.8 makes it nicer. Well, you'll find that the bullet without gravity would have hit 10cm higher, but with gravity it will actually be closer to the original target. I just put how much it falls by and the distance from the desired target as my answer.
Reply 5
Avatar for alex18127
alex18127
Original post by Zii
The sight is like the aimhole. Its where the gun was aiming.

you *******
Reply 6
Avatar for 1asdfff
1asdfff
2
can anyone do this?
Reply 7
Avatar for mqb2766
mqb2766
21
Original post by 1asdfff
can anyone do this?

After 13 years, I'd hope so. It sounds like a straightforward horizontal/vertical suvat projectile question.
Original post by mqb2766
After 13 years, I'd hope so. It sounds like a straightforward horizontal/vertical suvat projectile question.

You have been expelled from the F38 secret assassin society (emphasis mine).
Original post by DFranklin
You have been expelled from the F38 secret assassin society (emphasis mine).

Er... Maybe that should have been a private message...
Original post by DFranklin
You have been expelled from the F38 secret assassin society (emphasis mine).

The first rule of maths club is, don't talk about maths club.
Reply 11
Avatar for 1asdfff
1asdfff
2
Is the answer 8.11 cm, so gravity makes it 1.89 cm closer, or does it make the gun fire 8.11 cm closer?
Original post by 1asdfff
Is the answer 8.11 cm, so gravity makes it 1.89 cm closer, or does it make the gun fire 8.11 cm closer?

8.1 is the vertical distance?
Reply 13
Avatar for 1asdfff
1asdfff
2
Original post by mqb2766
8.1 is the vertical distance?

yeah should be 8.11 cm higher instead of 10 cm with gravity
Original post by 1asdfff
yeah should be 8.11 cm higher instead of 10 cm with gravity

The question states the sight was less than ideal.

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