## Yau Jong Twu

Yau Jong Twu Greenbelt, United States of America Yau-Jong Twu is a teacher at Eleanor Roosevelt High School in Greenbelt MD. She has been teaching the calculus-based AP Physics C since 1999 and the algebra-based AP Physics since 2003. Her AP Physics B / AP Physics 1 and 2 lesson videos are designed for students who have never had physics before. These videos are also used for "flipped classroom" teaching at Eleanor Roosevelt High School. Her AP Physics C lesson videos are designed for students who are at least taking pre-calculus concurrently. Please visit twuphysics.org for videos and supplemental material by topic.

## User videos

Gravitational Potential Energy
This lesson will review gravitational potential energy being MGY, where y is the height above a reference point on the ground. This lesson will look at an example to better understand the concept. Gravitational potential energy is related to the gravitational force between a person and the earth, and how a single object does not posses this kind of potential energy. This way of calculating the gravitational potential energy of an object planet system will only work if the gravitational field is uniform. An example will be shown to explain this.
Gravitational Potential Energy: Maximum Height
This lesson will take a look at a problem about what happens when an object is shot vertically upward from the surface of the moon and what initial speed is required to reach maximum height. Gravitational Potential energy will be looked at and shown how it relates to this concept of maximum height.
Gravitational Potential Energy: Escape Speed
This lesson will take a look at a projectile fired upward it would reach a maximum height and fall back down, the faster the initial speed the higher the projectile would go, if fired at a fast enough speed the object would keep going and not return with infinite height . This lesson looks at the minimal initial speed provided to an object to never come back is defined as escape speed. An example and diagram will be drawn to explain this concept.
Inertial Mass & Gravitational Mass
This lesson will look at Newton's 2nd law of motion to define mass as a measure of an object's inertia. With the same net force of an object, this lesson will explain how and why it is difficult to change an object's velocity or state of motion. Newton's law of gravitation will be reviewed and its relation to an objects weight. This lesson will use an example to better explain the concept.
Inertial Mass & Gravitational Mass: How to Measure
This lesson will explain how to measure an object's inertial and gravitational mass. This lesson will look at which Newton's law is needed to be able to solve for inertial mass. This lesson will look at inertial mass measurement and gravitational mass and will draw a diagram to better explain the concept. This lesson also takes a look at a video filmed in space by NASA discussing and showing mass.