# UCM on a skid pad

The Tesla Roadster is an all-electric sports car. It can accelerate from 0-60 mph in just 3.9 seconds, and has a top speed of 125 mph. The weight of the Roadster is 2700 pounds.

Joe drives his Roadster on a wide, flat pad of concrete. There is a circle of radius R = 50 m marked on the pad, and Joe tries to keep the car on the circle. He finds that he can drive at a maximum speed of v = 49 mph without skidding.

1. Convert the speed from 49 mph to meters per second.
2. What is the acceleration of the car?
3. What is the force of friction exerted by the concrete on the car?
4. What is the normal force exerted by the concrete on the car?
5. What is the coefficient of "skidding friction"?

Nosy aliens see Joe driving around and around in a circle. "Wow, this is cool!" they say. "We simply must show the Hendersons back home in Copernicus crater."

The aliens transport Joe, his car, and his concrete skid pad onto the Moon, where the local acceleration due to gravity is just one-sixth that on the Earth.

1. What is the normal force exerted by the concrete on the car now?
2. What is the maximum force of friction the concrete can exert on the car?
3. How fast can Joe drive in a circle now without skidding?

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