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

In summary, the conversation discussed a problem where Dave Johnson, a bronze medallist at the 1992 Olympic decathalon in Barcelona, had a vertical velocity component of 6 m/s at the high jump. The question was how far his center of mass moved up during the jump, and it was determined that gravity was the only force affecting his body. The solution involved finding the time and displacement, with a time of 0.612 seconds and a displacement of 3.67 meters.
  • #1
Gingerclaire_
6
0
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?
 
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  • #2
You only need to look at the vertical component of the motion.
 
  • #3
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​
 
  • #4
BvU said:
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.
 
  • #5
Anything in your recent past (lectures, for instance) or in the preceding pages of your textbook that might help ?
 
  • #6
We have been looking at Work, Energy & Power or Energy Conservation but I can't see anything relevant.
 
  • #7
How about gravity? Anything to do with dropping stuff off a cliff or out a window?
 
  • #8
Do you do a kinetic energy equation? Sorry I think I'm making it more difficult for myself here
 
  • #9
Gingerclaire_ said:
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?
 
  • #10
So there is a force acting upward - work. Am I right?
 
  • #11
Gingerclaire_ said:
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?
 
  • #12
Oh it is gravity then! So you work out time (t=0.612) and then find displacement (s=3.67)
 
  • #13
As always, show the units with you calculations.
 

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

1. What is projectile motion?

Projectile motion is the motion of an object that is projected or thrown into the air and moves along a curved path under the influence of gravity. It is a combination of horizontal and vertical motion.

2. What factors affect projectile motion?

The factors that affect projectile motion include the initial velocity, the angle of projection, the air resistance, and the gravitational force. These factors determine the shape and distance of the projectile's trajectory.

3. How is the trajectory of a projectile calculated?

The trajectory of a projectile can be calculated using the equations of motion, which take into account the initial velocity, the angle of projection, and the acceleration due to gravity. The trajectory can also be determined using mathematical models or by conducting experiments.

4. What is the difference between horizontal and vertical motion in projectile motion?

Horizontal motion in projectile motion refers to the motion of the object along the horizontal axis, which remains constant unless acted upon by an external force. Vertical motion, on the other hand, refers to the motion of the object along the vertical axis, which is affected by the force of gravity.

5. What are some real-life examples of projectile motion?

Some real-life examples of projectile motion include throwing a ball, shooting a basketball, launching a rocket, and throwing a javelin. These objects all follow a curved path due to the force of gravity acting upon them.

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