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Let's think about what physics is and what topics are covered in an introductory physics course.

Physics is built on a foundation of math and it seeks to explain all phenomena in the universe. It forms the basis for other sciences like chemistry and biology. Physics uses simple yet elegant math to …

Learn Introduction to high school physics Position, velocity, and speed Acceleration Interpreting motion data

If you’ve mastered this content and want to explore physics at the next level, we recommend our AP Physics 1 and AP Physics 2 courses. Give us feedback on this course

Khan Academy offers free, world-class education in physics, covering forces and motion topics.

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物理学研究的是决定我们身处的物质世界的基本原理。我们将从运动自身开始。然后，我们将在许多不同的实际情况中了解力、动量、能量和其它概念。为了更好地理解物理学，你需要有牢固的代数基础以 …

Learn physics using videos, articles, and NGSS-aligned practice exercises. Explore the fundamentals of motion and forces, non-contact interactions, energy, and waves.

That is a valid method for solving that problem. I was never taught Khan Academy's method in example 2 in my AP Physics I class, so the steps you took are what I would've done for that problem.