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High school physics · IGCSE · A-level · AP · IB

Free physics lessons that start with a question.

Most problems look hard because we haven't found the one idea inside them. We look for it together.

Video lessons and printable study sheets by Tiaotiao (跳跳学长), a Peking University graduate. The videos have English audio and subtitles. Everything is free. You don't need an account or an email address.

读得懂中文?每一讲都有中文学习单。看中文页 →

Lesson 8 · Change in velocity

Question

A ball hits the ground at 5 m/s and bounces up at 2 m/s. What is Δv?

The simple version

Down is +, so v₀ = +5 and vₜ = −2. Δv = −2 − 5 = −7 m/s, up.

A mistake I made

I did 5 − 2 = 3.

A sample notebook entry from Lesson 8. How Tiaotiao learns →
  • 10Kinematics lessons
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“There is no shortcut. Not one of the strong students I knew, in high school or at Peking University, got good grades without putting in a lot of time.”— Tiaotiao

How it works

  1. Watch the lesson. It is taught in Mandarin. On YouTube you can choose English audio or English subtitles.
  2. Download the study sheet. It's a free PDF with the key ideas, in English or Chinese.
  3. Try the practice questions. Then check your work against the answers.

Meet Tiaotiao

Tiaotiao graduated from Peking University and teaches high school physics on YouTube. In China, students know Tiaotiao as 跳跳学长.

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