Physics Blog- 1/10

We started out on Thursday answering questions Mr. Wirth asked us. They are probably important questions to remember for the midterm, so know the answers!!
1. What is the definition of work?
We said the answer is, force acting through a distance. The equation for work is W=fd and the units are J.
2. What is the equation for kinetic energy?
KE=1/2mv squared (i cant do exponents)
3. What is the definition of energy?
Energy is the ability to do work.
4. Give an example of gravitational potential energy.
Some examples are roller coasters, alpine skiing, and power plants.

The day before the snow day or wind day or whatever that was we graphed the PE of a golf ball as it fell. As the ball fell, the PE was transformed into KE, also known as the energy of motion. The equation for the KE of the golf ball as it fell is: vf squared = vi squared + 2ad.

In this equation, vi = 0, a= g (9.81), and d= the height of the golf ball.

So.....as PE changes to KE, use the equation vf squared = 2gh.

The sum of PE and KE is constant throughout the golf ball's drop. PE+KE=constant, or as PE is lost, KE is gained.

Then, we watched a video that showed how potential energy is gained as a roller coaster goes upward. When it goes down (the fun part), kinetic energy is gained and potential energy is lost. In order to regain the potential energy, the roller coaster will have to go back up again.

Then...we learned about internal energy, which = Q. Internal energy is the total KE and PE of all atoms and molecules, including chemical and nuclear PE. Another more commonly used name for internal energy is TEMPERATURE.

The total mechanical energy = the total KE and PE of an object due to its velocity and position.

Total energy=ET (the t is supposed to be a subscript but I can't do that either). ET is the mechanical energy + internal energy. The equation for ET is: ET=KE+PE+Q.

The law of Conservation of Energy says that the total energy of a closed system is constant. A closed system is where energy is not exchanged with its surroundings. There are no external forces, and no work is done on the system.

There is also a work-energy relationship. The amount of work done=the change in PE. The work done on an object= the change in ET.

One last equation we learned on Thursday is: W=change in PE + change in KE + change in Q. The change in Q = the amount of heat added to a system. Work done against friction is lost as heat.

Andd...in case anyone forgot, the homework was Worksheet #5. Also, remember to turn in ALL LABS from the first semester, even if you don't get credit for them.