Physics II – 11/4 No Warm-up today. Began in library.

Physics II –11/2 Work on projectile drag spreadsheets. Return test retakes & discuss answers. Use your launcher to determine C d of a light projectile –Increase launcher power to make drag more observable. –Measure V o at some chosen high power setting. Then measure launch height, and horizontal distance traveled. Conduct multiple trials to measure both V o and horizontal distance with greater accuracy. –Measure m & A. Assume that ρ=1.22kg/m 3. –Fiddle with C d until your graph matches your observations (of horizontal distance traveled, given the vertical drop from your release point to the floor). Calculate C d another way -- by dangling the projectile from a string that is suspended from a moving stick. The stick is moving with a horizontal velocity = v. Drag will cause the string to deviate from vertical by an angle = θ. Difficult Problems…

1.What would happen if you dug a hole through the center of the Earth, and then you jumped in? How long would it take you to fall to the center? What would happen then? Ignore air resistance. 2.Do you get wetter if you walk slowly in the rain, or if you run? How much wetter? Compare the volumes of water (in liters) that will smack into you at these two speeds, given the following assumptions… Assumptions: You (the thing getting wet) are a sphere with a radius of 0.5m. The distance you must travel horizontally in the rain, for a distance of one kilometer. Your “walking” pace is 1m/s. Your “running” pace is 5m/s. The raindrops are uniform spheres with diameters of 2mm. The drops are uniformly distributed in the air of them per cubic meter. The density of air is 1.22kg/m 3. The density of rain water is 1000kg/m 3