 My Math Forum Motion Equations: Velocity Eliminate time?
 User Name Remember Me? Password

 Physics Physics Forum

 August 8th, 2018, 04:17 AM #1 Senior Member   Joined: Oct 2015 From: Greece Posts: 137 Thanks: 8 Motion Equations: Velocity Eliminate time? I'm reading a Physics book and currently I'm in the Motion chapter. This chapter shows how you can calculate the motion equations. Below I'm going to give you a photo of what I did so far and inside a red rectangle you can see the equation which I can't calculate. The problem is to eliminate the time quantity for velocity's equation. I tried solving a second degree equation in order to find t and replace it into the velocity's equation, but I just could not solve it: Last edited by skipjack; August 8th, 2018 at 08:55 AM. August 8th, 2018, 04:41 AM #2 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,838 Thanks: 653 Math Focus: Yet to find out. Why not solve the first degree equation for $t$ instead? August 8th, 2018, 04:53 AM   #3
Senior Member

Joined: Oct 2015
From: Greece

Posts: 137
Thanks: 8

Quote:
 Originally Posted by Joppy Why not solve the first degree equation for $t$ instead?
LoL I'm stupid, forget about this thread   Why do I always think of the hard way first? And then getting so absorbed by it that I can't see there is a simpler way...

Last edited by skipjack; August 8th, 2018 at 08:55 AM. August 8th, 2018, 04:56 AM #4 Senior Member   Joined: Oct 2015 From: Greece Posts: 137 Thanks: 8 By the way just from curiosity, is there a way to find time by solving a second degree equation and taking all the 3 possibilities from the distinctive (<0, =0, >0)? Or it's impossible? If it's possible, I would like to see a solution. Last edited by skipjack; August 8th, 2018 at 08:56 AM. August 8th, 2018, 05:06 AM #5 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,838 Thanks: 653 Math Focus: Yet to find out. Yes a good exercise. You may actually find more insight into what the variables describe Thanks from babaliaris August 8th, 2018, 06:01 AM #6 Senior Member   Joined: Oct 2015 From: Greece Posts: 137 Thanks: 8 I did it!!! Can you take a look and answer my comments (inside the images)??? First Page: https://image.ibb.co/bRe6Dz/first.jpg Second Page: https://image.ibb.co/iD3Ytz/second.jpg Third Page: https://image.ibb.co/jX07Le/third.jpg Last edited by babaliaris; August 8th, 2018 at 06:04 AM. August 8th, 2018, 01:39 PM #7 Math Team   Joined: Jul 2011 From: Texas Posts: 3,016 Thanks: 1600 $v_f = v_0 + at \implies t = \dfrac{v_f-v_0}{a}$ $\Delta x = v_0 \cdot t + \dfrac{1}{2}at^2$ substitute for $t$ ... $\Delta x = v_0 \left(\dfrac{v_f-v_0}{a}\right) + \dfrac{a}{2} \left(\dfrac{v_f-v_0}{a}\right)^2$ $\Delta x = \dfrac{v_0v_f - v_0^2}{a} + \dfrac{a(v_f^2 - 2v_fv_0 + v_0^2)}{2a^2}$ $\Delta x = \dfrac{2v_0v_f - 2v_0^2}{2a} + \dfrac{v_f^2 - 2v_fv_0 + v_0^2}{2a}$ $\Delta x = \dfrac{2v_0v_f - 2v_0^2+v_f^2 - 2v_fv_0 + v_0^2}{2a}$ $2a \Delta x = v_f^2-v_0^2 \implies v_f^2 = v_0^2 + 2a \Delta x$ Thanks from babaliaris Tags eliminate, equations, motion, time, velocity Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post markosheehan Applied Math 2 September 13th, 2016 08:23 AM Usama Farooq Geometry 2 September 7th, 2015 04:32 PM kunz398 Calculus 2 May 14th, 2015 07:20 AM blueye89 Algebra 2 December 18th, 2012 05:34 PM Chikis Algebra 7 October 5th, 2012 10:03 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top      