0
$\begingroup$

I was given a problem where a man crouching on a diving board, he tilts forward until he tips off the board and rolls mid-air till he hits the water

My question is not about the problem, I can solve it. But there are no forces in the fall cause an angular acceleration?

What about air resistance? I mean I don't think he's reaching terminal velocity from a diving board.

Why won't air resistance have an effect on his angular acceleration? It should have a moment about his centre. And I assume that there are angles where the moments due to air resistance on opposite sides DO NOT cancel out.

Perhaps he is rolling too fast for this to be an issue and the moments due to air resistance approximately = 0 ?

Improve this question
$\endgroup$
1
  • $\begingroup$ Air resistance effect on the angular acceleration might be negligible. Real air resistance may cause angular acceleration at one half of the turn and deceleration at the other half. $\endgroup$ Commented Mar 16 at 13:36

1 Answer 1

Reset to default
1
$\begingroup$

What about air resistance? Why won't air resistance have an effect on his angular acceleration?

Because this is an introductory mechanics class, and introducing air resistance into the problem would make it an advanced mechanics problem.

What the author wants you to do is to neglect the effect of air resistance. Strip away the facts that it's a man, and that there's a diving board and water -- just do the calculations for a body with the given dimensions, that are undergoing the defined motions, and that the problem asks what the state of that body is when it touches a horizontal plane 30ft below its starting point.

If it's really troubling you, then calculate the speed of travel, and dig out the aerodynamic equations to see what the dynamic pressure is going to be. Then work out about how much force and torque there could possibly be on your diving guy. You'll probably find out that they're going to cause a negligible effect on the guy's angle when he hits the water. But even if you don't -- remember that three or four years from now, you'll have the grounding in the basics learned firmly enough that you'll be able to cope with real aerodynamics.

Improve this answer
$\endgroup$

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.