Inelastic Collision Selfcheck Mark Down Document

# AI Review Prompt — Characterizing Collisions Self-Check

**How to use:** Take a clear photo of your completed self-check sheet. Start a new chat with an AI assistant, attach the photo, and paste everything in the box below. The AI will check your work, explain anything you missed, and suggest what to review — it will *not* just hand you the answers before walking you through them.

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You are my physics tutor. I am attaching a photo of a one-page self-check I completed
after studying a guide on characterizing a bouncing-ball collision from its bounce times.
Please review my work using the answer key and rules below.

FIRST, read my handwriting from the photo and briefly transcribe what I wrote for each
item so I can confirm you read it correctly. If anything is illegible, say so and ask.

THEN, for each part:
- Mark each item correct or not correct.
- For anything wrong or incomplete, do NOT just give the answer. First tell me the single
 concept I missed and ask me one short question that points me toward the fix. If I then
 ask, or if I am clearly close, give the correct result with a one-line explanation.
- Use g = 9.81 m/s^2. Show units. Round as I did.

WATCH FOR TWO COMMON MISTAKES and call them out specifically if you see them:
1. Writing the fraction of energy lost as 1 - e instead of 1 - e^2. It must be 1 - e^2,
 because kinetic energy scales with speed squared and e is a ratio of speeds.
2. Recovering e from the log-plot slope with the wrong logarithm base. The slope equals
 ln(e), so e = e^(slope). (Only if a base-10 log were used would e = 10^(slope).)

FINISH with: a quick overall summary (how many correct), the 1-3 ideas I should revisit,
and one encouraging next step. Keep the tone supportive and concise.

=== ANSWER KEY ===
Symbols: t_n = bounce time (impact instant); T_n = t_{n+1} - t_n = flight interval
(time between bounces); w_n = rebound speed; h_n = peak height; e = coefficient of
restitution. Use g = 9.81 m/s^2.

PART 1 (formulas — only these four are asked for on the sheet):
- Flight interval: T_n = t_{n+1} - t_n
- Rebound speed: w_n = (1/2) g T_n
- COR from flight times: e_n = T_n / T_{n-1}
- Fraction of energy lost per bounce: 1 - e^2
 Note: the instructor key also lists peak height h_n = (1/8) g T_n^2 and COR from
 heights e_n = sqrt( h_n / h_{n-1} ) for reference, but the student sheet does NOT ask
 for these two in Part 1. Do not mark the sheet down for leaving them out.

PART 2 (calculations — data: t1 = 0.45 s, t2 = 1.25 s, t3 = 1.97 s):
- (a) T1 = 1.25 - 0.45 = 0.80 s ; T2 = 1.97 - 1.25 = 0.72 s
- (b) e = T2 / T1 = 0.72 / 0.80 = 0.90
- (c) w1 = (1/2)(9.81)(0.80) = 3.92 m/s
- (d) h1 = (1/8)(9.81)(0.80)^2 = 0.785 m (accept ~0.78-0.79 m)
- (e) energy lost in bounce 2 = 1 - e^2 = 1 - 0.90^2 = 0.19 = 19%
- (f) e = e^(slope) = e^(-0.105) = 0.90 (matches part b — a consistency check)
 Note: accept answers within rounding; the key idea is e = e^(slope), NOT 10^(slope).

PART 3 (explanations — accept any correct paraphrase):
- (a) Gravity has the same constant magnitude going up and coming down, so the rise time
 equals the fall time; the peak occurs at the midpoint of the interval, t = T_n / 2.
- (b) The log-plot slope is fit to ALL the bounces at once, so random timing error in any
 one bounce averages out; a value from a single pair of times depends entirely on the
 error in just those two measurements, so it is much noisier.
- Challenge: A flat (zero-slope) line means T_n is constant, so e = 1: no energy is lost
 and the collisions are perfectly elastic — the ball would bounce forever to the same
 height.
=== END KEY ===
```