Ch6_AronsonJ

=**Lesson 1-a.toc**=
 * 1) What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully.
 * 2) First, I understood that work occurs when a force acts on an object to cause displacement. For example, work occurs when I lift my backpack off of the ground and mount it on my shoulder. Second, I understood that work is equal to force times distance times theta (w=F* Δd* θ). For example, when a man of mass 65-kg pushes a cart 4 meters to his right, w=(9.8*65)(4)(1)=2548 J.
 * 3) What (specifically) did you read that you were a little confused/unclear/shaky about from class, but the reading helped to clarify? Describe the misconception you were having as well as your new understanding.
 * 4) From our class discussion, I was confused about which angle was actually theta. However, the reading helped to clarify that theta is the angle between force and displacement. For example, if a ball is rolled up an incline, the angle is that between the incline and the ground.
 * 5) What (specifically) did you read that you still don’t understand? Please word these in the form of a question.
 * 6) Which part of a force causes a horizontal displacement?
 * 7) What (specifically) did you read that was not gone over during class today?
 * 8) I read about negative work, which was not covered in class. Negative work occurs when a force acts upon an object to prevent displacement.

=Internal Forces vs. External Forces=

TRENDING: INTERNAL AND EXTERNAL FORCES

As reported by the Physics Classroom, forces can be categorized not only as contact forces or action-at-a-distance forces, but also as internal forces or external forces. Internal forces include gravity forces, magnetic force, electrical force and spring force, while external forces include applied force, normal force, tension force, friction force and air resistance force. External forces can change the total mechanical energy of an object, so they are also called “non-conservative forces.” Internal forces can change the form of energy without changing the total mechanical energy, so they are also called “conservative forces.” If the work done is positive work, then the object will gain energy, and if the work is negative work, then the object will lose energy.

Exercises:
 * 1) A ball falling from 2 meters high without air resistance is an example of gravitational potential energy to kinetic energy, because the ball is initially at rest and goes into motion once dropped.
 * 2) The skier gliding from A to B is kinetic energy to potential energy, because the skier is initially moving until he rests at point B.
 * 3) A baseball traveling upward towards a man in the bleachers is kinetic energy to potential energy, because the baseball is initially in motion until it rests in the hands of the man in the bleachers.
 * 4) A bungee cord beginning to exert an upward force on a falling jumper is elastic potential energy to kinetic energy, because the bungee cord exerted no initial force on the jumper until it had to do so.
 * 5) The spring of a dart gun exerting a force on a dart as it is launched from rest is elastic potential energy to kinetic energy, because it is initially a compressed spring but later expands to launch the dart.