## 20161015

### Physics midterm question: maximizing Pokémon Go pokémon spawns

Physics 205A Midterm 1, fall semester 2016
Cuesta College, San Luis Obispo, CA

Pokémon Go is an application that runs on a smartphone that can track your location[*]:
According to the game's code, it will spawn a pokémon for you every five minutes if you're not moving. But if you're walking, they'll spawn faster. Walk in a straight line if you can. The game checks in and measures your location periodically. Walking around the same block over and over won't net you many pokémon spawns.
Determine whether Pokémon Go is programmed to reward you with "many pokémon spawns" by tracking your average speed, or tracking the magnitude of your average velocity. Explain your reasoning using the properties of position, distance traveled, displacement, speed, and velocity.

[*] Patrick Allan, "Two Walking Tips Every Pokémon Go Trainer Needs to Know" (August 4, 2016) lifehacker.com/two-walking-tips-every-pokemon-go-trainer-needs-to-know-1784847638.

Solution and grading rubric:
• p:
Correct. Discusses/demonstrates understanding of:
1. distinction between magnitude of average velocity (displacement magnitude over the elapsed time), and between average speed (distance traveled over the elapsed time);
2. specifically compares "walking around the same block over and over" versus walking "in a straight line" to argue that:
1. "walking around the same block over and over" will result in a displacement magnitude that will be less than walking that same distance in a straight line, therefore Pokémon Go will "net you many pokémon spawns" by tracking your magnitude of average velocity, not your average speed; or
2. "walking around the same block over and over" will result in the same distance traveled as walking that same distance traveled in a straight line, therefore Pokémon Go does not track your average speed in order to "net you many pokémon spawns."
• r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
• t:
Nearly correct, but argument has conceptual errors, or is incomplete.
• v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
• x:
Implementation/application of ideas, but credit given for effort rather than merit.
• y:
Irrelevant discussion/effectively blank.
• z:
Blank.
Sections 70854, 70855, 73320
Exam code: midterm01br1Q
p: 38 students
r: 13 students
t: 5 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 3428):

Another sample "p" response (from student 6924):