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Acceleration Due to Gravity

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Jumping Buses

Jumping Buses

Credit: Laura Guerin
Source: CK-12 Foundation
License: CC BY-NC 3.0

The image here is of Evel Knievel jumping over 13 double decker buses. Evel Knievel successfully jumped over 13 buses in Wembley Stadium in 1975 by accurately calculating the velocity, launch angle and launch height.

Amazing But True!

Credit: Cliff from Arlington, Virginia, USA
Source: http://en.wikipedia.org/wiki/File:Evel_Knievel_and_Harley-Davidson_XR-750_at_Madame_Tussaud%27s_Las_Vegas_cropped.jpg
License: CC BY-NC 3.0

Evel Knievel performed his stunts on this 1972 Harley-Davidson XR-750 [Figure2]

As Evel Knievel sailed through the air, it is easy to see that he is traveling in two directions; both of which are perpendicular to each other. As Evel Knievel heads towards the ramp to jump the buses, he initial has a velocity in one direction. When he leaves the ramp, he has a velocity in two directions (which we will call the x-axis towards the buses and the y-axis will be defined as perpendicular to the buses). To have a velocity in both the x and y direction great enough to pass the buses, Mr. Knievel and his crew must calculate how much of his velocity will be lost due air resistance along the x-axis and due to the acceleration of gravity along the y-axis. 

The relationship and understanding between position and velocity along the x,y axis is fundamental to the understanding to every aspect of physics. From traveling to the moon, particles in an electric field, the motion of any body can be broken down into 3 dimensions.

Can You Apply It? 

  1. As Evel Knievel soared through the air, did gravity affect his motion along the x-axis, the y-axis, or both axes?
  2. What would be the optimal angle for someone who wanted to jump any object with a motorcycle, assuming that the landing platform is the same height as the launching platform?
  3. If someone attempted to break one of these record-breaking jumps with a flat ramp (causing the rider to leave the ramp parallel to the ground), would they be successful? If the answer is no, what could be done to make the jump successful without changing the angle of the ramp?

Image Attributions

  1. [1]^ Credit: Laura Guerin; Source: CK-12 Foundation; License: CC BY-NC 3.0
  2. [2]^ Credit: Cliff from Arlington, Virginia, USA; Source: http://en.wikipedia.org/wiki/File:Evel_Knievel_and_Harley-Davidson_XR-750_at_Madame_Tussaud%27s_Las_Vegas_cropped.jpg; License: CC BY-NC 3.0

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