Mechanics: Momentum and Collisions
Momentum and Collisions: Audio Guided Solution
Problem 28:
Jack D. Ripper flipped out after missing a Must-Do-It question for the third time on his Minds On Physics assignment. Outraged by the futility of his efforts, he flings a 4.0-gram pencil across the room. The pencil lodges into a 221.0-gram Sponge Bob doll which is at rest on a countertop. Once in motion, the pencil/doll combination slide a distance of 11.9 cm across the countertop before stopping. The coefficient of friction between the doll and the countertop is 0.325. Determine the speed at which the pencil is moving prior to striking Sponge Bob.
Audio Guided Solution
Editor's Note: In the audio solution, the post-collision speed of the doll is incorrectly reported as 0.758 m/s. This is the square of the post-collision speed. By taking the square root, the post-collision speed is found to be 0.8706 m/s. Subsequently, the answer reported in the audio file is incorrect. Click the show answer button below to view the correct answer. Sorry for the error.
Click to show or hide the answer!49 m/s
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 = 1.50 kg, vi = 2.68 m/s, F = 4.98 N, t = 0.133 s, vf = ???.
- 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.
Read About It!
Get more information on the topic of Momentum and Collisions at The Physics Classroom Tutorial.
- Momentum Conservation Principle
- Isolated Systems
- Collision Analysis
- Newton's Second Law
- Kinematic Equations
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