Physics 201 Test 2 practice Short Answer (4 points each) 1 What - - PDF document

Physics 201 Test 2 practice Short Answer (4 points each) 1 What is the other half of the action/reaction pair associated with the normal force of a table supporting a book? 2 Give an algebraic expression for the net force acting on a skydiver before and after he reaches terminal velocity. 3. When traveling around a sharp corner in a car, you are undergoing centripetal

• acceleration. Explain why it feels like you are being pulled toward the outside of the curve,

rather than toward the center. 4. A 6.1 kg physics book is sitting on the table with no external forces acting upon it other than gravity and the table. The coefficient of static friction between the table and the book is .55. What is the force of friction on the book? 6. What force component(s) allow a car to round a banked-turn at higher speed than a flat turn? Be sure to show a free-body diagram. 7. When Wilbur asks Mr. Ed to pull a cart of hay, Mr Ed responds “I’d like to, but the laws

• f physics won’t allow it. According to Newton’s 3rd law, if I pull on the wagon, it pulls back on

me with an equal force. Thus, the net force is zero and I can’t possibly move the cart”. Where is the fallacy in Mr. Ed’s argument? 8. Give at least two reasons why the gravitational force on an object may vary slightly from

• ne location on earth to another.

9. If only one force acts on an object, can it have zero acceleration? Can it have zero velocity?

Problems (10 pts each)

• 1. You are driving home at dusk from a ski trip in Vermont, along an snowy road that is at a 5

degree downslope. 350 feet ahead, a bear steps out of the woods into the road. Fortunately, you have new snow tires, with

s = .59 and k = .38. The speed limit is 55, but you are prudently

going 48 mph. Will you be able to stop in time if you slam on the brakes? How about if your car has anti-lock brakes? (Assume instant reflexes and show all your work)

• 2. A 3 gram rubberband has an elastic spring constant of 58 N/m. If each side of the rubber

band is stretched by 8 cm, and launched from ground level, what is the maximum height that the rubber band could fly if it were shot straight up ? (ignore air resistance)

• 3. After a large blizzard, workers at a Colorado ski area measured a coefficient of static friction
• f .92 between the old layer of compacted snow and the new fluffy snow. It was also known that

the kinetic coefficient of friction would be about .63. Will an avalanche occur on “Phat Sister”, their steepest slope (44 degree pitch, length 1.5 km)? How fast will the avalanche be moving at the bottom of the slope?

• 4. As a professional speed-skier, you are attempting to break the world-record for speed (251

km/hr). The ski-course is very long, has an average pitch of 47 degrees, and you have a mass of 78 kg. You have developed a brand-new wax that reduces

k to 0.12. You’ve also done your best

to minimize air resistance, but you still have a drag coefficient of .0955. The density of air is 1 kg/m3 and your cross section area is .8 m2. What is your final speed? Do you break the record?

• 5. You decide that you want to see how fast you must accelerate from a stoplight to keep your

physics book pinned against the flat front of your car’s bumper. The coefficient of static friction between book and bumper is .35 and the book has a drag coefficient of .23. After you have accelerated at this rate for 10 seconds, find your speed and determine how much you can reduce your acceleration while still keeping the book from falling.