
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 
Newbie 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. 
April 22nd, 2016, 02:37 AM  #2 
Senior Member Joined: Apr 2014 From: UK Posts: 779 Thanks: 292 
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) 

Tags 
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 