Ignoring air resistance, determine the time required for the package to hit the ground. The plane releases a “care package” that falls to the ground along a curved trajectory. The directions to the right and upward have been chosen as the positive directions. (© Stephen Dalton/Photo Researchers).įigure 3.9 shows an airplane moving horizontally with a constant velocity of +115 m/s at an altitude of 1050 m. In this time-lapse photograph, the cat exhibits projectile motion while in the air, assuming that the effects of air resistance can be ignored. Example 2 and other examples in this section illustrate how the equations of kinematics are applied to projectile motion.įigure 3.8 CONCEPTS AT A GLANCEIn projectile motion, the horizontal or x component of the acceleration is zero, and the vertical or y component of the acceleration is the acceleration due to gravity. In this text, then, the phrase “projectile motion” means that a x = 0 m/s 2 and a y equals the acceleration due to gravity, as the Concept-at-a-Glance chart in Figure 3.8 summarizes. If the path or trajectory of the projectile is near the earth’s surface, a y has a magnitude of 9.80 m/s 2. The y component of the acceleration a y is the downward acceleration due to gravity. As a result, the y component of the velocity v y is not constant, but changes. In the vertical or y direction, however, the projectile experiences the effect of gravity. Thus, the x component of the velocity remains constant at its initial value or v x = v 0 x, and the x component of the acceleration is a x = 0 m/s 2. In the horizontal or x direction, the moving object (the projectile) does not slow down in the absence of air resistance. The motion of the ball on its curving path into the stands is a common type of two-dimensional motion called “projectile motion.” A good description of such motion can often be obtained with the assumption that air resistance is absent.ĬONCEPTS AT A GLANCE Following the approach outlined in Figure 3.6, we consider the horizontal and vertical parts of the motion separately.
The biggest thrill in baseball is a home run.
0 kommentar(er)
