October 16, 2012

Physical Science A

Bellwork:
    1.  How does the time taken to do work affect how much power is required for the work?

    2.  If a student pushes on a cart with a force of 800 N for 120 seconds and the cart does not move,     how much work is done by the student?

Collect the simple machine explanations.  If you have not finished the explanation, you will not start the lab!  Please go to the desk on the side of the room and finish you explanations. 

Objectives
1. Explain why all mechanical systems require an external energy source to maintain their motion.

2. Compare the work, input force, output force, mechanical advantage, and efficiency of the six simple machines (pulley, lever, wheel and axle, screw, inclined plane, wedge).


Simple Machine Lab:  Gain a practical understanding of how pulleys and levers work using hands on activities.  We will work on the lab for the period today and finish tomorrow.  If you do not finish the lab tomorrow, you will be responsible for finishing the lab at lunch or in the morning on thursday.



Physics

Check and Go over the prelab.  Discuss the answers.

Friction Lab:
This lab will allow you to calculate the coefficients of static and kinetic friction.  This lab requires extreme care if you are to calculate the results correctly. 

The setup is designed to allow you to slowly increase the angle of the board.  By doing this you will also increase the force pulling the block down the incline.  The correlation is

                increased angle = increased down force

As the angle and force then increase, there will be an angle where the block begins to move due to the increase size of the down force.  It is at this exact angle where the down force is equal to the force of static friction. 

Secondly, you will set the board at an angle larger than the motion angle in part a.  You will then calculate the acceleration of the block as it moves down the incline.  The acceleration can then be used to calculate the coefficient of kinetic friction.