Today we worked on worksheets in groups to learn about work.

Today I learned:

Originally, the equation for work was W=FΔd. Today, the equation was changed to be W = |F||Δd|cosΘ. This new equation reflects the possibility of positive or negative work being done, which means that the object moves forward or backwards. Of course, all of this is relative depending on which way forward is set. Negative work means energy is lost (e.g. going forward but slowing down).

Net work is the total work being done on the system, including positive and negative work. A great example of this is pushing an object forward on a normal table: it includes the work done by the applied force and the work done by the friction force. The kinetic energy net work theorem (or work energy principle) is represented by Wnet = Ekb - Eka = ΔEk. The net change in energy is equal to the net work being done. This is similar to forces and kinematics, where measurements are vectors and there is a net vector in the end.

Today I realized that all of the work we had been doing before had been building up to energy. Kinematics was movement, which led to forces and changes in movement, and now we’re talking about the energy that causes the change in movement. The equations that were learned before still apply in energy, and were used in a few of the questions along with the energy equations. For example, in the worksheet today, one question required the use of W= 1/2 mv^2. It also required determining the friction force from the coefficient of static friction, and the displacement using one of the five kinematics equations. Kinematics, forces and energy were used in this problem.

Today I wondered:

In the example of pushing against the wall, no work is done. But if the wall had to resist the work, the positive and negative work should be quite large, yet the applied energy went to heat due to sweat. How can this be?

If kinematics lead to forces which lead to energy, will energy lead to electricity? Electricty is a way of transferring energy right?

Today I had an intriguing idea:

The idea of work in intuitive terms is different from work in physics terms. Work in intuitive terms is using energy, even if nothing is happening. In physics, it means that something useful must be done, for example moving an object. There is a similar misconception in forces and constant velocity. Constant velocity can be achived with no force (if there is no external forces acting on it), which is hard to believe from daily intuition that an object can keep moving forward if there is nothing moving it. Force is an acceleration, a change in velocity, and that is quite important just like how physics work must be useful work.

After Unit Reflection

This post connects to requirement #5a. This was the day where we learned about what work is, the equation, net work, and many other work concepts. This lesson was actually quite important, a lot of energy and thermodynamics concepts were built upon the idea of work.