THE INCLINED PLANE – A SIMPLE MACHINE（斜面-一个简单的机器）.pdf

THE INCLINED PLANE – A SIMPLE MACHINE LAB MECH14 From Laboratory of Elementary Physics, Westminster College INTRODUCTION Our industrial world makes much use of the principles of mechanics as exemplified in simple machines. Simple machines are defined in two principle categories, the inclined plane and the lever. The lever further, includes the pulley and the wheel-and axle and the inclined plane also includes the screw and the wedge. The applications of simple machines generally provide some benefit or advantage for doing work. In this experiment a car moving on an incline or ramp will be considered as a simple machine, which has many applications in our world, such as a truck hauling freight up a hill or using a ramp to load a heavy object on the back of a truck. The car and its load, W due to its weight, is pulled up the tilted plane at approximately constant velocity by a hanging weight, Pu . The magnitude of the hanging weight is then adjusted, now identified as Pd, so that the car moves down the tilted plane, again with approximately uniform motion. The actual mechanical advantage, AMA, is defined as the ratio of the load, W, lifted to the force pulling it up the plane. Thus we have AMA=W/P . ( 1) u The theoretical mechanical advantage TMA, is defined as the ratio of the load lifted to the force, F, that would be required to pull it up the plane (so parallel to the plane) if there were no friction, so TMA=W/F. (2) Let F be the force of the gravitational mass or weight W component down the plane equal and in opposite direction of F. P and P differ in u d magnitude from each other and from F or F because of force of friction f. The force of