SP24 Quiz 2

Instructions: Your task is to make a model in response to the prompts in the quiz below. Be sure to apply a model from this class and include the relevant diagram(s) for that model.

Phenomenon: Launching a Rock to Knock at a Friend's Window

It's late, and you'd like to get your best friend's attention without their parents noticing. Your friend's bedroom is on the second story, and you want to use a slingshot to launch a small rock to knock on their window.

The second-story window is 5.2 meters above the ground, and the height you shoot your slingshot from is 1.8 meters above the ground. Your rock has a mass of 0.2 kg. You can approximate the rubber band on the slingshot as a spring with a spring constant k=400 J/m².

You know that if the rock is moving too fast when it hits the window, you might break the glass. However, you do want to make sure the rock has enough energy to hit the window at all in order to make a noise.

Big question:How far back should you pull your slingshot in order for the rock to be traveling at only 2 m/s when it hits the window?You can assume that the rock is pulled back so that its change in height is insignificant- i.e. you can still say that the rock is released at 1.8 meters above the ground.

Use what you've learned in PHYS 2A so far to analyze this scenario.

1. It may help to draw a physical scenario diagram and an object interaction diagram.
2. Draw as many complete Energy Interaction Diagrams as necessary to model the scenario, including a written justification as to why the physical system is open / closed
3. Find a numerical answer to the Big Question or get as far as you can in that process.

Reminder: Include clear reasoning throughout your solution that justifies the choices you make.

Maybe useful information: A Joule is defined as: [J] = [(kg)(m²/s²)]

Ethermal = m Cp T	Ephase = m Hp	P =E / t
	Q + W = E
KETranslationsal = mv2	PEGraviational =mgy whereg = 10m/s2	PEElastic= kx2