As the temperature of the water in which the machine is suspended increases, what change will occur in the system?
A. Less of the apparatus will be in the water. B. The balloons will become less buoyant. C. Each balloon will deform into a shape that maximizes its surface area. D. The belt will no longer be in contact with the freely turning wheels.
Explanation:
B is the best answer. As the water temperature increases (at least at temperatures greater than 4˚C), the density of the water decreases. This is because water expands, resulting in a larger volume while maintaining the same mass. Because the volume of water increases, more of the apparatus will be submerged in the water, not less. This eliminates choice A. The balloon, at all temperatures, should mold (deform) its shape to minimize the impact of external forces. It will deform according to the external forces in an effort to balance them out. Because the balloon is in motion, it will deform to a shape that minimize resistance as it moves through the water, which is the shape of least surface area. This affords minimal resistance and minimal exchange with the environment, which eliminates choice C. Whether the water is warm or cool, the belt should still be bound to the freely turning wheels, as long as the tension in the belt does not decrease, so rule out choice D. Only choice B remains. The buoyant force on the balloon depends on the density of the medium and the volume submerged. Because water is less dense at higher temperatures, we predict that the buoyant force on the balloon decreases. However, the higher temperature will cause the balloon to expand, resulting in a larger submerged volume. This increases the buoyant force. Lastly, because the height of the water increases, the balloon will find itself underneath a higher, albeit less dense column of water. This increase in external pressure will reduce its volume and in doing so make it less buoyant. Overall, there are two arguments to support less buoyant and one argument to support more buoyant. There is no way to decide for sure. But that is the beauty of a multiple-choice exam. You arent looking for an absolutely perfect answer. You are seeking the best answer, and given that choices A, C, and D are not the best answers, choice B, despite some uncertainty, must be the best answer. The MCAT will have some questions with ambiguity, so it is important that you get to a point where you ignore the ambiguity and select the answer they want you to choose as quickly as possible, and then move on. The best answer is B.
That is one of the shadiest explanations I've ever read.
A. Less of the apparatus will be in the water. B. The balloons will become less buoyant. C. Each balloon will deform into a shape that maximizes its surface area. D. The belt will no longer be in contact with the freely turning wheels.
Explanation:
B is the best answer. As the water temperature increases (at least at temperatures greater than 4˚C), the density of the water decreases. This is because water expands, resulting in a larger volume while maintaining the same mass. Because the volume of water increases, more of the apparatus will be submerged in the water, not less. This eliminates choice A. The balloon, at all temperatures, should mold (deform) its shape to minimize the impact of external forces. It will deform according to the external forces in an effort to balance them out. Because the balloon is in motion, it will deform to a shape that minimize resistance as it moves through the water, which is the shape of least surface area. This affords minimal resistance and minimal exchange with the environment, which eliminates choice C. Whether the water is warm or cool, the belt should still be bound to the freely turning wheels, as long as the tension in the belt does not decrease, so rule out choice D. Only choice B remains. The buoyant force on the balloon depends on the density of the medium and the volume submerged. Because water is less dense at higher temperatures, we predict that the buoyant force on the balloon decreases. However, the higher temperature will cause the balloon to expand, resulting in a larger submerged volume. This increases the buoyant force. Lastly, because the height of the water increases, the balloon will find itself underneath a higher, albeit less dense column of water. This increase in external pressure will reduce its volume and in doing so make it less buoyant. Overall, there are two arguments to support less buoyant and one argument to support more buoyant. There is no way to decide for sure. But that is the beauty of a multiple-choice exam. You arent looking for an absolutely perfect answer. You are seeking the best answer, and given that choices A, C, and D are not the best answers, choice B, despite some uncertainty, must be the best answer. The MCAT will have some questions with ambiguity, so it is important that you get to a point where you ignore the ambiguity and select the answer they want you to choose as quickly as possible, and then move on. The best answer is B.
That is one of the shadiest explanations I've ever read.
