My Math Forum  

Go Back   My Math Forum > Math Forums > Academic Guidance

Academic Guidance Academic Guidance - Academic guidance for those pursuing a college degree... what college? Grad school? PhD help?

LinkBack Thread Tools Display Modes
April 22nd, 2016, 12:53 AM   #1
Joined: Apr 2016
From: Singapore

Posts: 1
Thanks: 0

Velocity of a projectile

Hi Guys,

First time post, I hope this is the correct location to post my 2 questions?

1/ I am trying to work out the horizontal distance a projectile will travel on level ground:

Resultant Velocity: 930m/s
Angle: 45deg
a: -9.81m/s2

I determined that Vx & Vy were 657m/s each.
I determined that tUp 67s, therefore tTotal was 134s

To calc the horizontal distance it should be just a matter of 134s x 657m/s (tTotal x Vx). Correct?

That gives me = 88,119m or 88km... this seems way off?

2/ Same projectile accelerates vertically (at 90deg from horizontal):

Total height
= sqr [ Vr2 / 2(-9.81m/s2) ]
= sqr [ (-930m/s)2 / ( -19.62m/s2) ]
= sqr [ -864,900m2/s2 / -19.62m/s2 ]
= sqr 44,082m
= 210m
Dist = 420m (seems too little to me??)

tUp = 930m/s / -8.91m/s2 = 94.8s
tTotal = 189.6s (3min 3s)

Again it only travels 420m vertically but takes 3min & 3s to travel...?

I cannot see any errors but the values don't look like they line up. I have been staring at this for 20m.

Any help would be really appreciated before I tear all my hair out. Thanks.

Last edited by skipjack; April 22nd, 2016 at 02:42 AM.
BioMechMan is offline  
April 22nd, 2016, 02:37 AM   #2
Senior Member
Joined: Apr 2014
From: UK

Posts: 965
Thanks: 342

1) Looks correct

2) After 1 second, the speed has dropped from 930m/s to 920.19m/s, so it must have travelled at least 920m in the first second alone, so yes, I think 420m is incorrect.
I see 44082m in your calculations, I get this number if I do 94.8 x 930/2 (flight time X average speed)
weirddave is offline  

  My Math Forum > Math Forums > Academic Guidance

projectile, velocity

Thread Tools
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
projectile motion, how to get the equation for range in projectile motion sweer6 New Users 4 May 21st, 2014 10:00 PM
projectile motion shalini maniarasan Calculus 1 April 25th, 2014 01:26 AM
Obtaining angular velocity given linear velocity and center of rotation 3D quarkz Calculus 0 April 18th, 2014 05:34 AM
Angle of projectile Canning_s Algebra 1 November 13th, 2010 11:43 AM
Projectile Motion symmetry Algebra 1 June 19th, 2007 10:26 PM

Copyright © 2019 My Math Forum. All rights reserved.