College

Avi, a gymnast, weighs 40 kg. She is jumping on a trampoline with a spring constant of [tex]$176,400 \frac{N}{m}$[/tex]. If she compresses the trampoline by 20 cm, how high should she reach?

Answer :

To solve this problem of how high Avi should reach when jumping on a trampoline, we need to use the concepts of energy conversion. Let's break it down step-by-step:

1. Understand the Problem:
- Avi's weight: 40 kg
- Spring constant of the trampoline: 176,400 N/m
- Compression distance of the trampoline: 20 cm (convert this to meters: 0.2 m)
- We want to find the maximum height Avi reaches after the jump.

2. Potential Energy Stored in the Trampoline:
- When Avi compresses the trampoline, she stores potential energy in it.
- The potential energy (PE) stored in a spring is calculated using the formula:

[tex]\[
\text{Potential Energy} = \frac{1}{2} \times \text{Spring Constant} \times (\text{Compression Distance})^2
\][/tex]

- Substituting the values we have:

[tex]\[
\text{Potential Energy} = \frac{1}{2} \times 176,400 \times (0.2)^2 = 3528 \text{ Joules}
\][/tex]

3. Conversion to Gravitational Potential Energy:
- At the maximum height, all of the elastic potential energy is converted into gravitational potential energy.
- Gravitational potential energy (GPE) can be calculated using:

[tex]\[
\text{Gravitational Potential Energy} = \text{mass} \times \text{gravitational acceleration} \times \text{height}
\][/tex]

- The gravitational acceleration (g) is approximately 9.81 m/s².
- Setting the potential energy equal to the gravitational potential energy, solve for height (h):

[tex]\[
3528 = 40 \times 9.81 \times h
\][/tex]

4. Calculate the Maximum Height:
- Rearrange the equation to solve for height (h):

[tex]\[
h = \frac{3528}{40 \times 9.81} \approx 8.99 \text{ meters}
\][/tex]

Therefore, Avi should reach a maximum height of approximately 8.99 meters. This is significantly higher than the given choice of 1.8 meters, indicating an alternative evaluation or context might be needed if this seems unexpected.