Circular Apertures and Resolution
(a) What is the minimum angular spread of a 633-nm wavelength He-Ne laser beam that is originally 1.00 mm in diameter? (b) If this laser is aimed at a mountain cliff 15.0 km away, how big will the illuminated spot be? (c) How big a spot would be illuminated on the moon, neglecting atmospheric effects? (This might be done to hit a corner reflector to measure the round-trip time and, hence, distance.)
Tractor Pull (Newton’s 2nd Law) Tractor Pulling is known as “the world’s heaviest motorsport.”- National Tractor Pullers Association (www.ntapull.com) Since 1967, Tractor Pull competitors from around the country have met at the Wood County Fairgrounds in Bowling Green, Ohio, for the National Tractor Pulling Championship (www.pulltown.com). For several summer days, the sounds of loud, supercharged engines fill the town. There are many competition categories, but the big ones are the 9,300 lb Super Farm Tractor and the Sign on I-75 (www.toledoblade.com) 20,000 lb Super Semi Truck categories. The tractor or truck attempts to pull a heavy weight (called the “sled”) as far as possible, up to the length of the track (320 feet). The mass on the sled slides back during the tractor pull, which changes the weight distribution and increases the frictional force on the sled, making it increasingly difficult for the tractor to pull the sled. There are four important forces acting on the sled during this event: The gravitational force (F )g acting on the sled from the Earth, the normal force (F ) exerted on the sled by the ground, the N kinetic friction force exerted on the sled by the ground (fk), and of course the tension (T) in the cable due to the pulling by the tractor. We have expressions for two of these forces: F g mg fk= k N Objective: By the end of this recitation, you should be able to (a) draw a free-body forc
