# Puzzling Adventures: Warmup #2 Solution

Solution to warm-up 2:
In the frame of reference of the disk, the shortest distances are straight lines. That is, the shortest path from one point on a circle to another is a straight-line segment. In general, the car will therefore traverse a chord through the disk such that the end of the chord is precisely the point where the car wants to exit given the disk's rotation. See this illustration:

http://cs.nyu.edu/cs/faculty/shasha/papers/eddyfig2car.doc

For example, if the car needs to go 130 degrees around the disk in the nonrotational frame, then it might be possible for the car to traverse a chord that subtends, say, 80 degrees at the same time the disk rotates 50 degrees.

That is, the fastest way to get from one point to the other in the disk is to aim the chord at a closer point and then let the disk swing the car around to the proper point.

http://cs.nyu.edu/cs/faculty/shasha/papers/eddyfig5car.doc

End of Warm-up 2

Back to Main Puzzle

You must sign in or register as a ScientificAmerican.com member to submit a comment.
Click one of the buttons below to register using an existing Social Account.

## More from Scientific American

• Climatewire | 22 minutes ago | 1

### Salt Spray May Prove Most Feasible Geoengineering

• Observations | 1 hour ago

### Can We Avert the End of Elephants?

• Extinction Countdown | 1 hour ago

### Lawsuit to Remove Plant from Endangered Species List Completely Backfires

• Scientific American Magazine | 2 hours ago

### 50, 100 & 150 Years Ago: Engineering Brings Water to Los Angeles, 1913

• Scientific American Mind | 3 hours ago | 5

## Latest from SA Blog Network

• ### Can We Avert the End of Elephants?

Observations | 2 hours ago
• ### Lawsuit to Remove Plant from Endangered Species List Completely Backfires

Extinction Countdown | 2 hours ago
• ### Is Elsevier really for-science? Or just for-profit?

Information Culture | 3 hours ago
• ### Ich probiere : Revisiting Abraham Flexner s dream of the useful pursuit of useless knowledge.

The Curious Wavefunction | 5 hours ago
• ### Nelson Mandela's Long and Hungered Walk To Freedom

Food Matters | 5 hours ago

## Science Jobs of the Week

X

Give a 1 year subscription as low as \$14.99

X

X

###### Welcome, . Do you have an existing ScientificAmerican.com account?

No, I would like to create a new account with my profile information.

X

Are you sure?

X