**Unit 5: Work, Energy and
Power**

**Problem Set C**

**Problem 10: **

A 843-kg roller coaster car is lifted to a height of 57.1 meters above the ground where it begins its descent from an initial rest position. A total of -14061 Joules of work are done on the car by air resistance as it descends the first hill and rises to the top of the first loop - a height of 16.2 m. What is its speed (in m/s) at the top of this loop?

- Read the problem carefully and diagram the physical situation (initial-final state diagram and/or work-energy bar chart)
- Identify known and unknown information in an organized manner (write on diagram)
- Take the time to plot out a strategy prior to beginning the solution (cancel terms in work-energy equation and perform conversions when necessary)
- Identify an appropriate formula to use
- Perform step-by-step algebraic manipulations

**0.5 • m • v _{i}^{2
}+ m • g • h _{i} + F • d • cos
_{ } =
0.5 • m • v_{f}^{2 }+ m • g • h
_{f}**

General information about work and energy problems is described on the Set C Overview page.

A detailed discussion of how to analyze physical situations using work-energy bar charts is provided online at The Physics Classroom.

A detailed description of the work-energy relationships for situation in which external forces are doing work is provided online at The Physics Classroom.

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