Forces in 2D Audio Guided Solution F2D13Q3

This problem represents a good illustration of how we can combine a Newton's Laws analysis with a kinematic analysis in order to determine a final answer. When I read the problem I notice that there's distance information, there's speed information that is mentioned in the problem, that's kinematic stuff, and then there's mass, force, and acceleration information, that's epinetical MA stuff. So, like any problem, read it carefully, identify that which you know, and draw a free body diagram, analyze the forces, and write an epinetical MA equation. Now, what we know is that it's an inclined plane problem, inclined with a theta of 32.8, we know m equals 68.8 kilograms, and we know on the kinematic side of the problem v original equals zero, and we also know, and this is a very important statement, that the hill is so high, 50.4 meters high. Now the motion, that's a vertical distance, the motion does not occur along the vertical, it occurs along the incline, and so you'll need to say d equals 50.4 meters divided by the sine of 32.8 degrees, that takes the height and changes it to a distance along the inclined plane, d is 50.4 divided by the sine of 32.8. Now, that's kinematic information, so kinematics wise we know v original, and we know d, and we're looking for v final, so the strategy will involve using epinetical MA to get an A, and then plugging into a kinematic equation to get a v final. So as we approach the epinetical MA part, that begins with a free body diagram, draw the forces on the skier, there is F grab down, F norm perpendicular to the inclined surface, the F grab down gets broken up into an F perpendicular, that balances F norm, into an F parallel that is unbalanced by any other force. So your F net is the F parallel part of gravity, it's mg sine theta, or 68.8 times 9.8 times the sine of 32.8 degrees. If you take that F net as mg sine theta and divide it by the m, you will get an acceleration value, and then once you get that, pick up kinematic equation that has within it the following four variables, vF, the unknown, and then the three knowns, A, v original, and d. Be careful with your algebra, and solve for vF, you can do it.