2-5

Today was a 2 hour delay so our class was shortened__*__
 * __Thursday February 6th, 2009__**
 * Agenda:** The Effects of Work Pre Lab

We began class by silently reading page 13: The Effects of Work on a System.

After reading Mr. Manning Posted questions on the board and gave us time to answer them. The questions and answers are as follows.

__Work to lift an Object__ 1.) Why is the displacement the same as the change in height? The object starts at an initial spot and the displacement is the height the object moved from the origional location. Xi = Hi Xf = Hf Example: The crane to the left has lifted the part from its initial position of zero on the ground to its new height. Therefore the displacement of the object is equal to the height.

2.) Why is the weight equal to the lifting force? Because it moves at a constant speed the forces on the box must be equal. 3.) Why is delta-h the same as h in most cases?\ Hi = 0 m It starts from a position of zero. 4.) If work was done to lift an object, what type of energy was changed? Gravitational Potential Energy/ Mechanical Energy

__Work to move an Object Horizontally- To make it speed up__ 5.) Where did the equation delta-x = v * t come from? -- v = (delta-x)/t is used in kinematics 6.) Show more math that proves that: m* ((Vf-Vi) / t) * ((Vf + Vi) / 2) *t) = m ((V^2t-V^2i) / 2) = m(( Vf-Vi) / 2) 7.) If work was done to push an object horizontally, what type of energy was changed? Kinetic Energy


 * Homework:** Energy Transformations paper is due Monday for extra credit