Velocity 2D question

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s4116792
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Homework Statement



If a long jumper at the top of his trajectory is moving at 6.5 m/s (horizontally) and his centre of mass is 1.1m abover where it was when he launched into the jump, how fast must he have been moving when he launched?


Homework Equations




Vx = Vox + ax*t

The Attempt at a Solution



In all texts i look at they say that the initial velocity should be the same as final velocity in the x-axis but that isn't the correct answer for the question in the text.

Thanks for any help.
 

Answers and Replies

  • #2
Nick89
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Ask yourself this:

Is there a force in the horizontal direction that could cause an acceleration or deceleration on the jumper?

If yes: A force is exerted on the jumper in the horizontal direction thus giving him an acceleration (either forward or backward) thus changing the speed.

If no: No force is exerted on the jumper in the horizontal direction, so the acceleratoin in the horizontal direction is 0, so the horizontal speed does not change.
 

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