Projectile Motion: Calculating Flight Time and Initial Speed

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Homework Help Overview

The discussion revolves around a projectile motion problem involving a rifle aimed horizontally at a target 50 meters away, with the bullet hitting 2.0 cm below the aim point. Participants are tasked with calculating the bullet's flight time and initial speed.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the time it takes for the bullet to drop 2 cm and question the information provided. Some express uncertainty about the equations needed to solve the problem, while others discuss unit conversions and the relationship between gravity, time, and position.

Discussion Status

Some participants have made progress in calculating the flight time, with one reporting a result of 0.064 seconds. There is ongoing exploration of how to determine the bullet's speed based on this time, with various equations being referenced and discussed.

Contextual Notes

Participants note the lack of explicit information regarding time and express frustration over the difficulty of the problem. There is mention of using equations from a textbook, but some participants feel uncertain about their application.

jarrellboog04
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A rifle is aimed horizontally at a target 50m away. The bullet hits the target 2.0cm below the aim point.

A. What was the bullet's fight time?
B. What was the bullet's speed as it left the barrel?

Please HELP!
 
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jarrellboog04 said:
A rifle is aimed horizontally at a target 50m away. The bullet hits the target 2.0cm below the aim point.

A. What was the bullet's fight time?
B. What was the bullet's speed as it left the barrel?

Please HELP!

Welcome to PF.

How long does it take to drop 2 cm?
 
It does not give that info
 
It does not give me the time
 
I have some equations but i am not sure how to use them
 
jarrellboog04 said:
It does not give me the time

Well then figure it out.

You know gravity.
You know the distance.
So ...
 
None of those are the equations i have for the problem i have the answer from the back of the book but that does not help if i do not no how to answer it i tried many differnet ways but still can not find the right way
 
jarrellboog04 said:
None of those are the equations i have for the problem i have the answer from the back of the book but that does not help if i do not no how to answer it i tried many differnet ways but still can not find the right way

Which of those equations relates gravity, time and position? That is of course if you dropped it from rest, Vo = 0?
 
  • #10
i changed the 2cm to .02m to get the same units
 
  • #11
jarrellboog04 said:
i changed the 2cm to .02m to get the same units

OK. That you have to do.

So which equation did you try?
 
  • #12
I did conversion. I jus figured out the answer to part a i got .064s
i used the equarition
y^f=y^i + (v^y)i delta (t)-1/2g(delta (t)2
 
  • #13
jarrellboog04 said:
I did conversion. I jus figured out the answer to part a i got .064s
i used the equarition
y^f=y^i + (v^y)i delta (t)-1/2g(delta (t)2

Right equation. Good result.

Now it traveled 50 m in that time.
How fast you figure it was going to do that?
 
  • #14
But now i am trying do part b but cant
 
  • #15
jarrellboog04 said:
But now i am trying do part b but cant

Now it traveled 50 m in that time.
How fast you figure it was going to do that?
 
  • #16
I am going to use this equation and see if i can figure it out
x^f=x^i+(v^x)i delta (t)
 
  • #17
jarrellboog04 said:
I am going to use this equation and see if i can figure it out
x^f=x^i+(v^x)i delta (t)

OK. that works. Xi is 0 of course.
 
  • #18
i got Xi to be .02m
 
  • #19
i got xi to .o2cm
 
  • #20
jarrellboog04 said:
i got Xi to be .02m

No. When it was aimed it was aimed toward 0. It dropped .02.
 
  • #21
u still can not figure it out
 
  • #22
jarrellboog04 said:
u still can not figure it out

Which component are you talking about?

The time times x-Velocity is 50m.

x-Velocity is 50m/.064s

This is not rocket science. Oh, wait a minute, it is.
 
  • #23
I meant to say i still can not fingure it out
 
  • #24
thanks
 
  • #25
this is hard
 

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