Relative Magnitudes of Forces - General Physics - Solved Past Paper, Exams of Physics

Download Relative Magnitudes of Forces - General Physics - Solved Past Paper and more Exams Physics in PDF only on Docsity! 2. (25 pts) a) (5 pts) You accidentally drop a frozen turkey on your foot. Comment on the relative magnitudes of the forces exerted on your foot (by the turkey) and on the turkey (by your foot). Accoring to Newton’s 3rd Law, the force exerted on your foot by the turkey has exactly the same magnitude as the force exerted on the turkey by your foot. (However, they are in opposite directions.) b) (5 pts) What aspect(s) of an oscillating spring/mass system determine the total energy? The total energy of an oscillating spring/mass system depends on the spring constant k and the ampli- tude of the motion A. c) (5 pts) For some reason, your little sister collects all of your textbooks and sits with them on your skate board. She then starts throwing the books. Explain why your sister (and the skate board) start to move in the direction opposite to that in which the book are being thrown. There are two possible answers to this. (1) As your sister exerts a force on the books to throw them, the books exert a force on your sister in the opposite direction which causes acceleration and starts her moving. (2) Since the momentum of the book/sister/skate board system is conserved, as the books move one way your sister/skate board must move the other way. d) (5 pts) A pendulum is transported from Earth to the new lunar base. Since the mass of the pendulum bob is the same on the moon as on the earth (or anywhere else, for that matter), will the astronauts still have to re-calibrate the period of the pendulum in order to continue using it to keep track of time on the moon? (i.e. is the period of the pendulum different on the moon from when it’s on the Earth?) Explain. Since the angular frequency of the pendulum depends on the length and the gravitational constant (but not the mass), moving it to the moon does affect the period (the gravitational acceleration near the surface of the moon is different than near the surface of the Earth). Thus they will have to adjust the calibration to keep time with the swinging pendulum. e) (5 pts) A suit case is dragged across the floor at a constant speed, yet friction is doing work on the suit case thus effectively removing energy from it. Explain how it is possible for the suit case to continue moving at a constant speed. Since it’s moving at a constant speed, the energy of the suit case is constant. If friction is draining energy out, there must be another force putting energy in (by doing work). This is the force exerted by whoever is dragging the suit case.