Physics 223

Physics 223 - Exam #4 - Final Exam
Fall 2011
Total Open Response Problem 1:____________/25
Total Open Response Problem 2:____________/25
Total Open Response Problem 3:____________/25
Total Open Response Problem 4:____________/25
Total Points:__________________________/100
Percentage Score:______________________
***Answer all four problems! Each problem requires you to show all the steps in obtaining your
answer. This includes, but is not limited to, defining all variables, showing/working the
equations to be used, and including units with all values listed. All problems are worth up to 25
points each. Good Luck!!!!
1) A light spring with a spring constant of 90.0 N/m rests vertically on a table, as shown in
illustration A. A 2.00 g balloon is filled with helium to a diameter of 1.0m and connected to the
spring, causing the spring to stretch; as shown in illustration B. The magnitude of the force
within the spring that pulls it back toward its unstretched position is equal to kDx (the Spring
Force). Recall that the volume of a sphere is 4/3 p r3. How much does the spring stretch
when the system is in equilibrium?
2) A drip-less candle (which means that the wax evaporates as the candle burns) is weighted
slightly on the bottom so that it floats upright in a container of water as illustrated. Describe
what happens as the candle burns. Be sure to label the free-body diagram to illustrate your
3) A copper wire (Y = 11 x 1010 Pa) of length 2.2 m and a steel wire (Y = 20 x 1010 Pa) of
length 1.6 m, both of diameter 3.0 mm, are connected end-to-end. When stretched by a force,
the total elongation is found to be 0.70 mm. Determine the force.
4) A liquid with a density of 1.65x103 kg/m3 flows through two horizontal sections of tubing
joined end to end. as shown in the figure below. In the first section, the cross-sectional area is
10.0 cm2, the flow speed is 275 cm/s (VY), and the pressure is 1.20x105 Pa. In the second
section, the cross-sectional area is 2.50 cm2.
a) Calculate the flow speed in the smaller section (VU)
b) Calculate the pressure in the smaller section.
c) Imagine that some water squirts from tiny leaks at points Y and U. Which squirt
shoots highest (or is there a tie)?