A military helicopter dropa BOMB


by Fanjoni
Tags: bomb, dropa, helicopter, military
Fanjoni
Fanjoni is offline
#1
Oct8-06, 08:01 PM
P: 11
A military helicopter on a training mission is flying horizontally at a speed of 65.0 m/s and accidentally drops a bomb (fortunately not armed) at an elevation of 250 m. You can ignore air resistance.

How much time is required for the bomb to reach the earth?(s)

How far does it travel horizontally while falling?(km)

Find the horizontal and vertical components of its velocity just before it strikes the earth.(m/s)

If the velocity of the helicopter remains constant, where is the helicopter when the bomb hits the ground? height above ground(m)
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d_leet
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#2
Oct8-06, 08:03 PM
P: 1,076
You need to show us some work first before we can help you. What have you tried so far, where are you getting stuck?
007banshee
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#3
Oct8-06, 08:07 PM
P: 4
Use regular kinematics formulas and you'll be fine

Fanjoni
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#4
Oct8-06, 08:08 PM
P: 11

A military helicopter dropa BOMB


so far i have founf the time for the bomb to fall which is 7.14s using x=VT+gT^2/2
I also found how far it travels which is .464km

But i dont know how to find the vertical and horizontal components and where the helicopter is when the bomb hits the ground
Agnostic
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#5
Oct8-06, 08:14 PM
P: 112
Now calculate the horizontal velocity from horizontal distance and time

and

the vertical velocity from vertical distance and time
Fanjoni
Fanjoni is offline
#6
Oct8-06, 08:17 PM
P: 11
would the horizontal componant be 65m/s and the vertical component be 70.04m/s

I am not sure i f it is right
drpizza
drpizza is offline
#7
Oct8-06, 09:26 PM
P: 291
Without grabbing a calculator, 70.04 sounds reasonable after doing some mental math (I usually use g=10m/s^2; after 7 seconds, the velocity is 70 m/s down, average velocity is 35 m/s down and distance is 7s*35m/s = 245 meters down; so your answer sounds quite reasonable.)

You could have also used v_f^2 = v_i^2 + 2ad for the velocity calculation, rather than relying on that intermediate step (although the time was asked for, so you had to find it anyway.)

If you have a physics teacher with a nice sense of humor, point out that the helicopter is going to follow the bomb all the way to the ground if there's no air resistance :)
drpizza
drpizza is offline
#8
Oct8-06, 09:31 PM
P: 291
I'm on dial-up, so I'm not going to wait 14 minutes for this video to load. However, I think it's the correct video that I use in class to demonstrate the answer to your question. Hopefully it helps you understand the independence of horizontal and vertical velocities. i.e. note where the bombs are as they fall in relationship to where they came out of the B-52. This isn't a star trek model where everything is hanging from strings and the background is moving... :)

http://www.danshistory.com/b52.html


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