October 15, 2012
Physical Science A

Bellwork:
    1.  What does the mechanical advantage of a machine indicate?  If the value of the mechanical     advantage is less than 1, what does that indicate about the machine?

    2.  How does the amount of work done compare for the following situations:
        a.  Climbing a ladder up to a loft.
        b.  Walking up a plank up to the same loft. 

    3.  IF a situation requires 1200 J of work to perform, which will require more power, if the work is done     quickly or slowly?


Activity: Which requires more work?  Determine which situation requires more work, the steep slope or the low slope?

Discuss machines, mechanical advantage, and efficiency.

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).

HW:  Simple Machines:  You will have to research all six types of simple machines.  For each type of simple machine you should: explain how it works, the different types of each, how to increase the mechanical advantage, and how to decrease the mechanical advantage. 

For this assignment I will expect a drawing of each type of machine, followed by a paragraph explanation for each type of simple machine.

The simple machine explanation will be collected tomorrow. 

Also, you will have to fix the problems that you have gotten wrong on your quiz.  This will be due on wed.


Physics

Bellwork:
    1.  If a 23 kg bird feeder is hung in the middle of a 6 meter rope that is strung between two trees.  If     the feeder pulls the rope down .34 meters, what is the tension in the ropes that are supporting the     feeder?

    2.  What is the force of kinetic friction between a 80 kg box and the floor is the coefficient of friction is     .4?

Go over the home work.  Discuss the answer and method involved in solving the friction and statics problems.

Discuss the force of gravity and incline plane problems. 

HW:  Friction prelab and be sure you have read chapter 4 and also read chapter 5.  Do the
questions 35, 36, 37 in chapter 4 and 2,4,6,9,13,14,17-21 in chapter 5.