PHY 121 Exam 2 March 23 2026 Do not turn the pages of the exam until you are instructed to do so Exam rules You may use only a writing instrument while taking this test You may not consult any calculators computers books nor each other Problems 1 and 10 must be answered on the scantron form Problems 11 and 12 must be answered in exam booklet 1 Problem 13 must be answered in exam booklet 2 The answers need to be well motivated and expressed in terms of the variables used in the problem You will receive partial credit where appropriate but only when we can read your solution Answers that are not motivated will not receive any credit even if correct At the end of the exam you must hand in your exam the scantron form the blue exam booklets and the equation sheet All items must be clearly labeled with your name your student ID number and the day time location of your workshop If any of these items are missing we will not grade your exam and you will receive a score of 0 points You are required to complete the following Honor Pledge for Exams Copy and sign the pledge before starting your exam I affirm that I will not give or receive any unauthorized help on this exam and that all work will be my own Name Signature Page 1 PHY 121 Exam 2 March 23 2026 Page 2 PHY 121 Exam 2 March 23 2026 Problem 1 2 5 points Answer on Scantron form A person who weighs 450 N stands on a scale in an elevator The scale will read zero if 1 the elevator is accelerating up at 9 8 m s2 2 the elevator is moving at a constant speed of 9 8 m s 3 the elevator is accelerating down at 9 8 m s2 4 The scale will never read zero Problem 2 2 5 points Answer on Scantron form Two satellites orbit the Earth in circular orbits of the same radius One satellite is twice as massive as the other Which statement is correct about the speeds of the satellites 1 The heavier satellite moves twice as fast as the lighter one 2 The two satellites have the same speed 3 The lighter satellite moves twice as fast as the heavier one 4 The ratio of their speeds depends on the details of how they were launched Problem 3 2 5 points Answer on Scantron form Two stones one twice the mass of the other are dropped from a cliff Just before hitting the ground what is the kinetic energy of the heavy stone compared to the light one 1 1 4 as much 2 1 2 as much 3 The same 4 2 times as much 5 4 times as much Page 3 PHY 121 Exam 2 March 23 2026 Problem 4 2 5 points Answer on Scantron form A ball is thrown straight up Neglecting air resistance which statement is NOT true regarding the energy of the ball You can ignore the effect of the drag force 1 The potential energy decreases while the ball is going up 2 The kinetic energy decreases while the ball is going up 3 The sum of the kinetic energy and the potential energy is constant 4 The potential energy decreases when the ball is coming down 5 The kinetic energy increases when the ball is coming down Problem 5 2 5 points Answer on Scantron form If all three collisions shown in Fig 1 are totally inelastic which collision s causes the most damage Figure 1 Totally inelastic collisions 1 Collision I 2 Collision II 3 Collision III 4 Collisions I and II 5 Collisions I and III 6 Collisions II and III 7 Collisions I II and III Page 4 PHY 121 Exam 2 March 23 2026 Problem 6 2 5 points Answer on Scantron form Figure 2 shows the paths of two colliding steel balls Figure 2 The collision between two steel balls Which set of arrows shown in Fig 3 best represents the direction of the change in the linear momentum of each ball Figure 3 The change in the linear momenta of the two colliding steel balls 1 a 2 b 3 c 4 d 5 e Page 5 PHY 121 Exam 2 March 23 2026 Problem 7 2 5 points Figure 4 shows a roller coaster car at 4 different positions along its track Answer on Scantron form Figure 4 A roller coaster At which position is the kinetic energy of the roller coaster car the largest Assume there is no friction between the car and the track and that the effect of drag forces can be ignored 1 Position 1 2 Position 2 3 Position 3 4 Position 4 Page 6 PHY 121 Exam 2 March 23 2026 Problem 8 2 5 points Answer on Scantron form Figure 5 shows a potential energy distribution U x as a function of x Figure 5 Potential energy U as function of position x At what point does the force F associated with this potential energy distribution have its greatest magnitude 1 Point A 2 Point B 3 Point C 4 Point D 5 Point E 6 Point F 7 Point G Page 7 PHY 121 Exam 2 March 23 2026 Problem 9 2 5 points Answer on Scantron form A delivery man carries a packge as shown in Fig 6 Figure 6 Delivering a package He walks up the stairs to the second floor at constant speed A and along the hall at a constant speed B He accelerates to a run C and then moves at a greater speed along the hall D During what portions of the motion is the delivery man doing work on the package 1 A only 2 B only 3 C only 4 D only 5 A and C only 6 B and C only 7 None of these portions 8 Work is done throughout Page 8 PHY 121 Exam 2 March 23 2026 Problem 10 2 5 points Answer on Scantron form In what year were the Delta Werken completed Figure 7 The Oosterschelde kering 1 1953 2 1965 3 1971 4 1982 5 1997 6 2001 7 2010 8 2017 9 2025 Page 9 PHY 121 Exam 2 March 23 2026 Problem 11 25 points Answer in booklet 1 Several planets Jupiter Uranus Saturn possess nearly circular surrounding rings per haps composed of material that failed to form a satellite In addition many galaxies contain ring like structures Consider a homogeneous ring of mass M and radius R as shown in Fig 8 Figure 8 A homogeneous ring of matter exerting a force of particle m a 5 points What is the direction of the gravitational force exerted by the ring on a particle of mass m located a distance x from the center of the ring along its axis as shown in Fig 8 Make sure you motivate your answer b 5 points What is the magnitude of the gravitational force exerted by the ring on the particle when it is located a distance x …