Pebble Shot with Spring Constant - how to setup?

Click For Summary

Homework Help Overview

The problem involves a pebble being shot vertically using a catapult, with specific parameters including the mass of the pebble, the spring constant of the catapult, and the initial stretch of the spring. The goal is to determine the maximum height the pebble reaches above its starting point, while ignoring air resistance.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the conversion of elastic potential energy to gravitational potential energy and question how to relate these forms of energy to find the height reached by the pebble.

Discussion Status

Some participants have provided calculations for elastic potential energy and gravitational potential energy, while others are exploring the relationship between these energies and the height. There is an ongoing exchange of ideas regarding the formulas involved and how to apply them to find the height.

Contextual Notes

Participants are working under the assumption that air resistance can be ignored and are focused on the energy transformations involved in the problem.

Schoomy
Messages
42
Reaction score
0

Homework Statement


You shoot a 49 g pebble straight up with a catapult whose spring constant is 320 N/m. The catapult is initially stretched by 0.30 m. How high above the starting point does the pebble fly? Ignore air resistance.


Homework Equations


Unsure?


The Attempt at a Solution


49g pebble = 0.049kg
 
Physics news on Phys.org
When the spring is stretched how much elastic potential energy does it have?

This is the energy that is converted to gravitational potential energy to raise it to the maximum height.
 
Uelastic = (.5)(320N/m)(0.3m2) = 14.4.

But then what? How do I turn this into a height?
 
what is the formula for gravitational potential energy?
 
Ugrav = mg[tex]\Delta[/tex]y
 
I can find U grav, but i don't see what that would get me?

Ug = (0.049kg)(9.8)(0.3)
= 0.144
 
Schoomy said:
I can find U grav, but i don't see what that would get me?

Ug = (0.049kg)(9.8)(0.3)
= 0.144

0.3 is not the height. if y is the height and U=mgy, and you know the energy it has is equal to the elastic potential energy (which you found to be 14.4J) can you find the height y?
 
Yep. It was y that I was looking for...duh. So I just leave it blank, set Ug equal to 14.4, and solve for y, giving me roughly 30m as an answer.

Thanks!
 

Similar threads

Calculating spring constant of a spring loaded cannon
  • · Replies 7 ·
Replies
7
Views
4K
Spring constant, find height of projectile
  • · Replies 4 ·
Replies
4
Views
5K
Calculating Height of a Pebbled Launched by a Catapult
  • · Replies 1 ·
Replies
1
Views
6K
How Is the Spring Constant Calculated from Work Done?
  • · Replies 10 ·
Replies
10
Views
13K
Determining the Spring Constant for a Pendulum with a Spring-Loaded Launcher
  • · Replies 3 ·
Replies
3
Views
2K
Calculating Spring Constant and Energy Conservation: How Fast Will the Bag Drop?
  • · Replies 3 ·
Replies
3
Views
1K
How do you know when k in Hooke's law is positive or negativ
  • · Replies 2 ·
Replies
2
Views
3K
How Does Gravity Affect the Velocity of a Block on a Spring?
  • · Replies 6 ·
Replies
6
Views
2K
What is the stretch of the spring?
  • · Replies 7 ·
Replies
7
Views
15K
Finding Spring Constant for Rotational Motion Problem
  • · Replies 1 ·
Replies
1
Views
2K