Center of Mass and Torque | MCAT Physics Prep

Need help preparing for the MCAT physics section? MedSchoolCoach expert, Ken Tao, will teach you what you need to know about Center of Mass and Torque of Forces. Watch this video to learn how to do well on the physics section of the MCAT exam! The center of mass of an object is the point around which the mass of an object is equally distributed. Consider a cafeteria tray with your lunch placed on it. If you stack all the food in one corner and carry the tray with one hand under the center of the tray, the tray will be much more likely to slip out of your hand. However, if you distribute the food around the tray so that they are balanced around the center, the tray will feel much less likely to tip out of your hand. For the MCAT, there is a simple equation that allows us to calculate the center of mass for a one-dimensional system. Multiplying the mass of each object by its distance from an origin, summing those together, and dividing by the sum of all masses yields the center of mass of a tray. Objects will rotate about their center of mass, for instance, consider what would happen if you threw a hammer spinning through the air. A hammer is a metal head on a wooden stick. The metal head is much heavier than the stick handle, so the center of mass is closer to the metal head. If the hammer rotated while flying through the air, it would rotate around a point much closer to the metal end. Center of Mass Example What would be the center of mass of a hammer made of a 0.5 m long, 2 kg stick attached to a 3 kg metal head? We are interested in determining the point along the length of the hammer the center of mass would be located. From the question stem, we can identify two discrete masses: the wooden stick and the metal head. Each mass will act at its particular center of mass along the length of the hammer. The center of mass of the stick is at 0.25 m along its length, so it will contribute 2 kg of mass at 0.25 m. The hammer will contribute 3 kg of mass at the end of the stick, 0.5 m along its length. We can calculate the center of mass by plugging these values into our equation for center of mass, from which we arrive at a value for center of mass of 0.4 meters. Torque Torque is a twisting force that causes the rotation of an object fixed around a point. For example, the blades of a windmill rotate around a fixed point. The torque resultant from a force is equal to r x F x sin(θ). In this equation, F is the force, while r is the lever arm, defined as the distance between the point of rotation and the point at which the force is applied. θ is the angle between the force vector and the lever arm vector. Note that in contrast to forces, which can cause motion in all sorts of directions, torque only causes rotation in the clockwise direction or counterclockwise direction. MEDSCHOOLCOACH To watch more MCAT video tutorials like this and have access to study scheduling, progress tracking, flashcard and question bank, download MCAT Prep by MedSchoolCoach IOS Link: https://play.google.com/store/apps/de... Apple Link: https://apps.apple.com/us/app/mcat-pr... #medschoolcoach #MCATprep #MCATstudytools