Solving Johnny's Swing Height Puzzle: Can You Get 1.4 Meters?

Click For Summary

Homework Help Overview

The problem involves calculating the maximum height of a swing based on the kinetic and potential energy of Johnny, who is swinging at a specific velocity and height above the ground. The subject area pertains to energy conservation principles in physics.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between kinetic energy and potential energy, with one participant attempting to equate the two to find the maximum height. There is a suggestion to show working to clarify the calculations involved.

Discussion Status

The discussion is ongoing, with some participants providing calculations and confirming the approach. There is a recognition of differing results, with one participant noting a height of 1.37 meters based on their calculations.

Contextual Notes

Participants are working under the assumption that energy is conserved and are using standard gravitational acceleration. There is a mention of specific values for mass and velocity, but the exact method for reaching the desired height remains a point of exploration.

Speedking96
Messages
104
Reaction score
0

Homework Statement



Johnny is swinging (on a swing) at a velocity of 4m/s when he is 56 cm above the ground. What is his maximum height?

Johnny is 45 Kg.

Homework Equations



Pe = mgh
Ke= (1/2)(m* v^2)
Total energy= Pe + Ke

The Attempt at a Solution



I tried setting the Ke equal to the Pe, but I get 0.81 Meters. However, I know that the correct answer is around 1.4 Meters.

I would like to know how to get 1.4 Meters.
 
Physics news on Phys.org
At 45cm he has some PE and some KE.
At the max height all of that is converted into PE.

I get 1.37m if I use g = 9.81

I suggest you show your working.
 
Okay. So, what you are saying is:

Pe: (9.81)(45)(0.56) + Ke: (1/2)(45)(4^2)

Then you plug all of that in for Pe and solve for height.

Thanks a bunch.
 
Correct.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
3K
Replies
13
Views
4K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
21
Views
3K
  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K