Ruth's Ramblings

Wayne's friend, a physics prof, is here to visit this weekend... anyone from UCLA ever take Physics 6A last spring? If so, you'll remember these midterm and final problems (these are real physics problems he put on his midterm and final):

Problem 4 (25 points):
Wayne is standing at rest and holding a snowball in his hand, while Ruth is running toward him at a constant speed. At the instant they are separated by 15 m, Wayne throws the snowball in Ruth's direction, releasing the snowball with a speed of 10 m/s at an angle of 60 degrees above the horizontal. The snowball is thrown from a height of 1. m above the ground and Ruth is 1.7 m tall. Amazingly, the snowball hits Ruth on the head as it falls! (Note: The snowball travels less than 15 m in the horizontal direction.)

a) For how long is the snowball in motion? (10 points)
b) How fast is Ruth running toward Wayne? (15 points)

I was a little bummed that I'm the one getting hit with the snowball -- I would have liked for the situation to be reversed. Oh well. Here's another problem from his final later that quarter:

Problem 2: "The Newlyweds" (25 points)
Wayne and Ruth (the snowball-throwing couple featured in Midterm 1 are now enjoying their fun-filled, physics-themed honyemoon in Hawaii. Let's follow them along. =)

a) First, Wayne and Ruth take a 5-hour flight from San Francisco to Honolulu, a distance of 2400 miles. They wait two hours in Honolulu for their 30-minute flight to Maui, a distance of 100 miles. What is their average speed during this trip in meters per second? (Include the waiting time in Honolulu, and note that 1 mi = 1609 m.) (8 points)
b) Next, Ruth decides to try suba diving off the coast of Maui. At what depth is the gauge pressure of sea water equal to 15 percent of the normal atmospheric pressure? (Normal atmosphereic pressure is 1.01 x 10(5) Pa, and the density of sea water is 1024 kg/m3.) (8 points)
c) Finally, at dinnertime, Ruth sits 1 m due north of Wayne, while a waiter stands 0.8 m from Ruth in a direction 30 degrees south of west. If Ruth's mass is 60 kg, Wayne's mass is 65 kg, and the waiter's mass is 80 kg, calculate the center-of-mass coordinates of this trio as measured by Ruth. (9 points)

Posted by Ruth at 10/26/2002