The Open Door Web Site
HOME PAGE BIOLOGY CHEMISTRY PHYSICS ELECTRONICS HISTORY HISTORY of SCI & TECH MATH STUDIES LEARN FRENCH STUDY GUIDE PHOTO GALLERY
ATOMIC and NUCLEAR ELECTRICITY and MAGNETISM MEASUREMENTS MECHANICS OPTICS PRACTICAL WORK QUESTIONS RELATIVITY THERMAL PHYSICS WAVES
MECHANICS
Google
Custom Search
Representing Motion Graphically
Displacement Against Time Graphs (s/t graphs)  
   
   
In this graph:  
 
the lines, a, represent stationary bodies  
   
the lines, b, represent motion with uniform (constant) velocity  
   
     
   
This graph represents accelerated motion  
   
If the acceleration is uniform then the curve is parabolic since s a t2  
   
The slope of an s/t graph represents velocity  
   
     
Velocity Against Time Graphs (v/t graphs)  
   
   
In this graph:  
   
the line, a, represents uniform velocity  
   
the lines, b, represent uniform acceleration  
   
   
     
   
The lines on this graph represent non-uniform accelerations  
   
   
The slope of a v/t graph represents acceleration  
   
v/t graph for a body in free fall  
   
     
Using a v/t Graph to Find Distance Moved (or Displacement)  
   
Here, the body moved with constant velocity  
   
During the 8s period shown, it is clear that the body moved  
   
8 10 = 80m  
   
   
     
In this case, the body was accelerating, uniformly, so the average speed during the 6s period was  
   
15/2 = 7.5ms-1  
   
therefore, the distance moved was  
   
7.5 6 = 45m  
     
Notice that, in each case, the arithmetic needed to find the distance moved by the body is equivalent to finding the area between the line and the time axis.  
     
   
   
area of rectangle = base height  
   
   
   
   
   
     
   
   
   
area of rectangle = (base height)  
   
   
   
   
     
In these simple cases, this observation changes nothing about the calculation needed to find the distance moved by the body  
     
   
   
However, if the shape of the graph is more complicated, as shown here, the only way to find the distance moved might be to draw the graph and measure the area under the curve (or more likely ask a computer to do it for you).  
   
   
   
The following graph represents a situation in which the sense of the motion of the body changed  
 
Combining the areas between the graph and the time axis, we have  
   
  A1 = +12  
  A2 = +12  
  A3 = -1  
  A4 = -6  
 
This means that the body moved a total distance of 31m.  
   
However, because of the change in the sense of the motion at t = 6s, the final displacement of the body at t = 10s, from its position at t = 0, is (24 - 7)m = 17m  in the positive sense.  
SITE MAP
WHAT'S NEW
ABOUT
PRIVACY
COPYRIGHT
SPONSORSHIP
DONATIONS
ADVERTISING
 

© The Open Door Team
2016
Any questions or
problems regarding
this site should be
addressed to
the webmaster

David Hoult 2017

Hosted By
Web Hosting by HostCentric

 
SiteLock
 
 
Mechanics Index Page