How Far Does Dave Johnson's Center of Mass Move Up During the High Jump?

[Gingerclaire_]

Dave Johnson, the bronze medallist at the 1992 Olympic decathalon in Barcelona, leaves the ground at the high jump with vertical velocity component 6 m/s. How far does his center of mass move up as he makes the jump?

 

[nasu]

You only need to look at the vertical component of the motion.

 

[BvU]

Hello Ginger, welcome to PF :)

Nice exercise. Somewhere along the line the template fell away. It's use is mandatory for good reasons. (Read the guidelines).

In this case you posted only the problem statement. What equations, tools, stuff have you available to tackle it ? Place them under 2). And what have you tried and what came out ? Put that under 3). Help is on the way...

1. Homework Statement
2. Homework Equations
3. The Attempt at a Solution​

 

[Gingerclaire_]

Hello Ginger, welcome to PF :)

Nice exercise. Somewhere along the line the template fell away. It's use is mandatory for good reasons. (Read the guidelines).

In this case you posted only the problem statement. What equations, tools, stuff have you available to tackle it ? Place them under 2). And what have you tried and what came out ? Put that under 3). Help is on the way...

1. Homework Statement
2. Homework Equations
3. The Attempt at a Solution​

I'm not sure about equations but I've no idea where to start with a solution.

 

[BvU]

Anything in your recent past (lectures, for instance) or in the preceding pages of your textbook that might help ?

 

[Gingerclaire_]

We have been looking at Work, Energy & Power or Energy Conservation but I can't see anything relevant.

 

[SteamKing]

How about gravity? Anything to do with dropping stuff off a cliff or out a window?

 

[Gingerclaire_]

Do you do a kinetic energy equation? Sorry I think I'm making it more difficult for myself here

 

[SteamKing]

Do you do a kinetic energy equation? Sorry I think I'm making it more difficult for myself here

A guy jumps off the ground. What forces are working on him so he doesn't go into orbit around the earth?

If you throw a ball up in the air, why does it come back down to the ground?

 

[Gingerclaire_]

So there is a force acting upward - work. Am I right?

 

[SteamKing]

So there is a force acting upward - work. Am I right?

Work is not a force. Once the jumper leaves the ground, there is only one thing affecting his body. What is it? If you pick up a book and drop it on the floor, why does the book fall?

 

[Gingerclaire_]

Oh it is gravity then! So you work out time (t=0.612) and then find displacement (s=3.67)

 

[SteamKing]

As always, show the units with you calculations.