## Thursday, November 18, 2010

### Thursday, November 18

We started the class by going over the homwork.

The homework problem was:
Eugenia slowly lifts a box by exerting a constant force of 5n. She moves the box from the ground up onto the table, which is 1m high.

Here are the questions on the homework:
1. Draw a picture of intial and final state for the box while she is lifting it.

2. Calculate the work Eugenia has to do in order to lift the box onto the table.

3. Dicuss the energy transformation and write a number sentence to express what occured.

4. Suppose Exerted a larger amount of force on the box at the beginning. What would she have to do to get the box to stop when it got to the table?

We also discussed this question:
Mary rides in an elevator from the first floor to the third floor. Answer the following questions.

Here are the questins:
1. Sketch the intial and final states, and then identify the system.

2. Make a reasonable approximation for the force applied and the distance between the floors in the building.

3. Write an integer statement for the work the elevator does to lift mary to the 3rd floor. Find the work.

4. How much work would the elevator have to do if marys twin sister joined her?

5. How much work would the elevator have to do if mary decided to go to the 4th floor instead? (find the work for both cases: with and without her sister)

-SA