# Mechanics: Circular Motion and Gravitation

## Circular Motion and Gravitation: Audio Guided Solution

#### Problem 27:

In 2009, NASA's Messenger spacecraft became the second spacecraft to orbit the planet Mercury. The spacecraft orbited at a height of 125 miles above Mercury's surface. Determine the orbital speed and orbital period of Messenger. (GIVEN: RMercury = 2.44 x 106 m; MMercury = 3.30 x 1023 kg; 1 mi = 1609 m)

## Audio Guided Solution

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## Habits of an Effective Problem Solver

• Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
• Identify the known and unknown quantities in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., m = 61.7 kg, v= 18.5 m/s, R = 30.9 m, Fnorm = ???.
• Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
• Identify the appropriate formula(s) to use.
• Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.