Charge 是甚麼?

## 物理、悟理 #9 - Rotational inertia

Webb, what is rotational inertia?

Webb, what is the difference between inertia and rotational inertia?

## 物理、悟理 #8 - Rotational motion

Webb, what is the rotational motion?

Webb, what is the difference between linear motion and rotational motion?

Webb, 旋轉運動有甚麼特別的?

## 物理、悟理 #7 - Free Body Diagram

Webb, 為什麼我算力學的題目，總是少考慮一些力?

Webb, 要怎樣才能將所有的受力考慮周全?

Webb, free body diagram 要怎麼畫才好?

## 《AP Calculus》A plane flies horizontally at an altitude....Find the rate of the plan travels at some time

Question:

A plane flies horizontally at an altitude of 5 km and passes directly over a tracking telescope on the ground. When the angle of elevation is π/3, this angle is decreasing at a rate of π/6 rad/min. How fast is the plane traveling at that time?

Solutions:

## 物理、悟理#6 - Vector and Scalar

Webb, what is vector and what is scalar?

Webb, how can I know velocity belong to vector or scalar?

Webb, what's the difference between these two words?