Hello Work and Energy!

B and E Blocks took their forces and laws of motion exam and will get a start on the concepts of work and energy on Monday, with E Block conducting an investigation on conservation of energy. The preliminary questions for the lab that you are working on for homework will introduce you to the relevant ideas for the lab and give you some tools to interpret the results. B Block will engage in a discussion of work and kinetic energy and how they relate through the work-kinetic theorem.

C Block started their work discussion today. The scientific use of the term "work" was highlighted as was the formula we use to calculate work. Remember that the force in the formula is the net force acting on the object and the work assessed will be the next work the object experiences. Positive net force delivers positive work and negative net force delivers negative work. What this can mean is that an object speeds up (+work) or slows down (-work), starts from rest, comes to a stop, or changes direction. But, there must be some displacement for work to be done by that force and, further, the force must have at least some component in the plane of the motion for it to contribute to work. So, for a box sliding across the floor, gravity does no work on the box since the motion is purely horizontal, but weight acts vertically. Because work can produce a change of velocity, it can produce a change in kinetic energy the amount of that change is equal to the work done on or by the object. The work-kinetic energy theorem lets you assess work by measuring velocity changes or use a work value to predict a resulting velocity change for an object. We'll add another energy to our list on Monday, gravitational potential energy and add several more as the year goes on.

F Block conducted an investigation concerning conservation of energy with a ball tossed in the air. You were able to see the patterns of kinetic energy and gravitational potential energy change for the ball in free fall and those changes matched what we would predict based on what we know about free-fall motion. The energy graphs nicely showed that as kinetic energy decreased, gravitational potential increases and vice versa so that the total energy in the system remained constant. For your conclusion section, make sure to include the Extension piece with the bouncing ball (is conservation of energy observed for the bouncing ball - why or why not) and what we would have observed for a high bounce ball in the same situation. On Monday, we will begin our discussion of work and energy and use the lab for that lecture and subsequent ones to illustrate our points.

Have a good weekend!