# Mechanics: 1-Dimensional Kinematics

## 1-Dimensional Kinematics: Audio Guided Solution

#### Extra Problem 7:

A 438-m long train is moving on a straight track with a speed of 87.7 km/hr. The engineer applies the brakes at a crossing and later the caboose passes the crossing with a speed of 19.0 km/hr. Assuming constant acceleration, determine the length of time (in seconds) that the train blocks the crossing. Disregard the width of the crossing.

## Audio Guided Solution

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## Habits of an Effective Problem Solver

An effective problem solver by habit approaches a physics problem in a manner that reflects a collection of disciplined habits. An effective problem-solver...

• ...reads the problem carefully and develops a mental picture of the physical situation. If needed, they sketch a simple diagram of the physical situation to help visualize it.
• ...identifies the known and unknown quantities in an organized manner, often times recording them on the diagram iteself. They equate given values to the symbols used to represent the corresponding quantity (e.g., vo = 0 m/s; a = 4.2 m/s/s; vf = 22.9 m/s; d = ???.).
• ...plots a strategy for solving for the unknown quantity; the strategy will typically center around the use of physics equations be heavily dependent upon an understaning of physics principles.
• ...identifies the appropriate formula(s) to use, often times writing them down. Where needed, they perform the needed conversion of quantities into the proper unit.
• ...performs substitutions and algebraic manipulations in order to solve for the unknown quantity.