AP物理2 单元练习题1 Fluids and Thermal Physics.pdf

AP2 Fluids A cart full of water travels horizontally on a frictionless track with initial ve- locity v . As shown in the diagram, in the back wall of the cart there is a small v opening near the bottom of the wall that allows water to stream out. Consid- ering just the cart itself (and not the water inside it), which of the following most accurately describes the characteristics of the cart? Speed Kinetic Energy (A) stays the same stays the same (B) increases increases (C) stays the same increases (D) increases stays the same Answer: B As the water streams out of the cart, the water is pushed out of the cart by pressure from above, exerting a reactionary force pushing the cart and its contents forward, increasing the speed of the cart. As the speed of the cart is increas- ing, and its mass remains the same, the kinetic energy of the cart must also increase. EK: 3.A.4 If one object exerts a force on a second object, the second object always exerts a force of equal magnitude on the first object in the opposite direction. 3.E.1 The change in the kinetic energy of an object depends on the force exerted on the object and on the displacement of the object during the interval that the force is exerted. 5.A.2 For all systems under all circumstances, energy, charge, linear momentum, and angular momentum are conserved. For an isolated or a closed system, conserved quantities are constant. An open system is one that exchanges any conserved quantity with its surroundings. SP: 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. 7.2 The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. LO: 3.A.4.1 The student is