
Physics Physics Forum 
 LinkBack  Thread Tools  Display Modes 
April 30th, 2015, 07:11 AM  #1 
Senior Member Joined: Feb 2014 From: Louisiana Posts: 156 Thanks: 6 Math Focus: algebra and the calculus  Is v in kinetic energy formula speed or velocity?
I know that kinetic energy is a scalar quantity and thus only has a magnitude, so does this mean that v in (1/2)mv^2 is speed and not velocity?

April 30th, 2015, 07:28 AM  #2 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 1,884 Thanks: 610 Math Focus: Physics, mathematical modelling, numerical and computational solutions 
It doesn't matter because the square of the velocity is actually a dotproduct. $\displaystyle KE = \frac{1}{2} m \vec{v}^2 = \frac{1}{2} m \vec{v} \cdot \vec{v} = \frac{1}{2} m \leftv\right^2$ The vector notation is a little sloppy, but I hope you get the point. 
April 30th, 2015, 07:44 AM  #3 
Math Team Joined: Dec 2013 From: Colombia Posts: 6,446 Thanks: 2118 Math Focus: Mainly analysis and algebra 
As Benit says, the $v^2$ is $\vec{v}\cdot\vec{v} = \bigv\big^2$ which is the magnitude of the velocity squared or the dot product of the velocity with itself. Either way it's a scalar value with no direction. In practical terms, yes it's the speed. This should make sense, because energy doesn't have a directional component either. 

Tags 
energy, formula, kinetic, speed, velocity 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Kinetic and potential energy of an object  Mr Davis 97  Physics  3  April 20th, 2015 05:39 PM 
How was the formula for kinetic energy found, and who found it?  Ganesh Ujwal  Physics  3  January 5th, 2015 02:58 AM 
On The Energy Formula  Anamitra Palit  Physics  3  October 2nd, 2012 11:58 PM 
Find a twopart formula for the velocity v(t) that is valid  sivela  Calculus  1  January 27th, 2010 03:50 AM 
Find velocity, acc, and speed of particle?  remeday86  Calculus  2  March 7th, 2009 07:24 PM 