Dd Physics 2210 Fall 2011 David Ailion EXAM 2 PLEASE FILL IN THE INFORMATION BELOW: Name (printed): Name (signed): Student ID Number (unid): u Discussion Instructor: Marc Lindley Jon Paul Lundquist Peter Peroncik Rhett Zollinger Useful Information: 1 ft = 12 in (exact) 1 m = 3.28 ft 1 mile = 5280 ft (exact) 1 hour = 3600 sec = 60 min (exact) 1 day = 24 hr (exact) g earth = 9.80 m/s 2 = 32.2 ft/s 2 g moon = 1.67 m/s 2 = 5.48 ft/s2 1 year = 365.25 days 1 kg = 0.0685 slug 1 N = 0.225 pound 1 horsepower = 550 ft pounds/s (exact) M earth = 5.98 10 24 kg R earth = 6.38 10 3 km M sun = 1.99 10 30 kg R sun = 6.96 10 8 m M moon = 7.35 10 22 kg R moon = 1.74 10 3 km G = 6.67 10-11 N m 2 /kg 2 k = 8.99 10 9 N m 2 /C 2 ε o = 8.85 10-12 F/m e electron charge = -1.60 10-19 C m electron = 9.11 10-31 kg
Dd Physics 2210 Fall 2011 David Ailion Name: Unid: Discussion TA: Exam 2 1 SHOW ALL WORK!! Place a circle or box around each answer. Specify units for each answer. Report all numbers to three significant figures. Circle all that apply! A. [5 pts.] Two metal balls are the same size but one weighs twice as much as the other. The balls are both dropped from a height of 5.0 meters towards the ground and are released simultaneously. Which of the following must be true (neglecting air drag) about the balls during the time they are falling. (Circle all that apply.) 1. The lighter ball starts out moving faster than the heavier ball. 2. The heavier ball has an acceleration that is half as large as that of the lighter ball. 3. The Earth exerts a gravitational force on the heavy ball that is twice as large as that on the lighter ball. 4. The Earth exerts an equal gravitational force on both balls. 5. The heavy ball exerts a force on the Earth that is twice as large as the force on the Earth exerted by the lighter ball. 6. None of the above are true. B. [5 pts.] Which of the following must be true for an object that has a constant non-zero speed? (Circle all that apply.) 1. The object is moving in a circle. 2. The object is moving in a straight line. 3. The object has zero acceleration. 4. The tangential component of the object s acceleration is zero. 5. The radial component of the object s acceleration is zero. 6. None of the above are true. C. [5 pts.] A roller coaster car has a mass of 500 kg when fully loaded with passengers. The car passes over a hill of radius of curvature r (r = 15 m) as shown. At the top of the hill the car has a speed of 8.0 m/s. Calculate the force of the track on the car at the top of the hill. Give magnitude and direction. D. [5 pts.] Three boxes are pushed across a frictionless horizontal surface as shown. Suppose we compare the force F 2,5 that mass 2m exerts on mass 5 m with the force F 5,10 that mass 5 m exerts on mass 10 m and with the applied force F. Circle the correct answer. 1. F 2,5 = F 5,0 = F 2. F 2,5 = F > F 5,10 3. F > F 2,5 = F 5,10 4. F > F 2,5 > F 5,10 5. F > F 5,10 > F 2,5
ate the angle between vector B and C in part C. Dd Physics 2210 Fall 2011 David Ailion Name: Unid: Discussion TA: Exam 2 2 SHOW ALL WORK!! Place a circle or box around each answer. Specify units for each answer. Report all numbers to three significant figures. A bullet is fired at a small stationary animal 200 m away. The animal is at exactly the same height as the gun, which you can assume to be on the ground. (a) (b) (c) [8 pts.] In order to hit the animal, the bullet is fired at an angle of 60 with respect to the horizontal. What is the initial speed of the bullet as it leaves the barrel? Assume that there is no wind. [6 pts.] Now, assume that the animal is moving away from the hunter at 8.0 m/s. If the shooter uses the same gun, ammunition and firing angle as in part (a), by how much will he miss the animal? [6 pts.] Suppose that, in addition to the motion described in part (b), the animal has a velocity component perpendicular to the line joining the hunter and the initial position of the animal. Furthermore, this velocity component is also equal to 8.0 m/s. See figure below. By how much will the bullet miss the target? Side View Top View
Physics 2210 Fall 2011 David Ailion Name: Unid: Discussion TA: Exam 2 3 SHOW ALL WORK!! Place a circle or box around each answer. Specify units for each answer. Report all numbers to three significant figures. A popular pastime is to see who can push an object closest of the edge of a table without it going off. You push the 100 g object and release it 50 cm from the table edge. The object slides across, sails off the edge, falls 1.0 m to the floor, and lands 30 cm from the edge of the table. Assume that the coefficient of kinetic friction, μ k, equals 0.50 and that of static friction, μ s, equals 0.75. (a) (b) [10 pts.] Calculate the speed of the object as it leaves the table. [10 pts.] Calculate the speed of the object at the moment you release it.
Physics 2210 Fall 2011 David Ailion Name: Unid: Discussion TA: Exam 2 4 SHOW ALL WORK!! Place a circle or box around each answer. Specify units for each answer. Report all numbers to three significant figures. A car accelerates down a hill going from rest to 30 m/s in 6.2 s. A toy consisting of a ball of mass m = 0.15 kg hangs by a string from the car s ceiling. The car s acceleration is such that the string remains perpendicular to the car s ceiling (which is assumed to be flat and parallel to the slope of the hill. (a) [10 pts.] Determine the angle θ. (b) [10 pts.] Calculate the tension T in the string.
Physics 2210 Fall 2011 David Ailion Name: Unid: Discussion TA: Exam 2 5 SHOW ALL WORK!! Place a circle or box around each answer. Specify units for each answer. Report all numbers to three significant figures. A person of mass m is standing on the floor of an amusement park ride with his back against the wall. The amusement park ride consists of a cylinder of radius R that spins about a vertical axis. When the cylinder achieves a sufficiently large rotation speed, the floor is removed but the person remains stuck to the wall. Assume that the coefficient of kinetic friction is μ k and the coefficient of static friction is μ s. (a) (b) [10 pts.] Calculate in terms of given quantities the maximum period of revolution of the cylinder necessary to keep the person from falling. [10 pts.] Suppose that suddenly a malfunction occurs and the cylinder s period doubles from the value in part (a). Calculate in terms of given quantities the time that the person takes to fall a distance d into the pit below. Assume that the person is in contact with the wall at all times.