Constants   Equations   Subjects   Periodic Table   Conversions   SI Units   Symbols Science Subjects Physics : Forces and Motion - Straight Line Motion Category Select   Key Words Displacement is the distance moved in a specific direction, measured in metres (m) Speed is the rate of change of distance, measured in metres per second (m s-1) Velocity is the rate of change of displacement, measured in metres per second (m s-1) Acceleration is the rate of change of velocity, measured in metres per second per second (m s-2)   Equations of Motion           Where a is acceleration (m s-2), u is the initial velocity (m s-1), v is the final velocity (m s-1), t is time (s) and s is displacement (m).   Velocity-Time/Displacement/Time Graphs Graphs of velocity/time and displacement/time can be drawn:     These graphs show the change of displacement (vertical, above the ground) and velocity of a ball thrown directly upwards (with negligable air resistance and acted upon only by the force of gravity). It can be seen that at the point where the ball is released, the velocity is maximum and displacement is zero. As the ball rises, the force of gravity acts upon it and reduces it's velocity and the rate of change of displacement decreases. The point where the ball is at it's highest point, the displacement doesn't change and so velocity is zero. The ball then begins to fall - the velocity increases until it impacts with the ground with maximum velocity.   From the displacement/time graph, you can calculate the velocity of the object by finding the gradient (change in displacement divided by the change in time) of the graph. From the velocity/time graph, you can calculate the acceleration of the object by finding the gradient (change in velocity divided by the change in time) of the graph, or you can calculate the displacement of the object by finding the area under the graph.     If you have anything to contribute, simply e-mail it to me at science@tcaep.co.uk. I look foward to hearing from you!

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