3. (20%) A hanging copper wire with a diameter of 2 mm has an initial length of 3 m and hangs vertically from the ceiling of your dorm room. When a 5 kg mass is attached to its end, the wire stretches by 0.425 mm; when a 10 kg mass is attached to its end, the wire stretches by 0.85 mm. The density of copper is 9 g/cm3 and one mole has a mass of 63 g. Find the approximate value of the effective spring stiffness of the inter-atomic force. Explain your analysis and any assumptions you may have made.
4. (15%) In the software download area of the Physics 141 web site (located at http://teacher.pas.rochester.edu/phy141/Software/SoftwareIndex.htm) you will find two movies that shows someone tossing a ball in an elevator that is moving up (ElevatorMovie1.mov and ElevatorMovie2.mov). Use Logger Pro to analyze the motion of the ball in both movies and answer the following questions:
a. What is the acceleration of the ball in each toss? In ElevatorMovie1.mov you will only be able to examine one toss, while in ElevatorMovie2.mov you will be able to examine multiple tosses.
b. What can you say about the difference in the motion of the elevators in the two movies?
5. (Optional; 25% extra credit) Place a spacecraft of mass 15000 kg at a location 10 Earth radii to the left of the center of the Earth and give it an initial velocity as shown in the Figure.
Let it coast, subject only to the gravitational attraction of the Earth, whose mass is 6 × 1024 kg. Plot a trail behind the spacecraft so that you can see the shape of the trajectory. At each step in the iteration, check for the spacecraft being closer than one Earth radius from the center of the Earth, and stop the program if that happens.
Note: Submit the actual programs via email to Professor Wolfs (firstname.lastname@example.org). The name of the file(s) should start with hw03p05XXYYYYYYYY where XX are your initials and YYYYYYYY is your student id number and the subject of your email should start with hw03p05XXYYYYYYYY.
Last updated on Monday, September 26, 2016 8:41