These concepts are merely an outgrowth of Newton's second law as discussed in an earlier unit. And if the velocity of the object is changed, then the momentum of the object is changed. Either way, a force will change the velocity of an object. If a force acts in the same direction as the object's motion, then the force speeds the object up. If the force acts opposite the object's motion, it slows the object down. Put another way, an unbalanced force always accelerates an object - either speeding it up or slowing it down. Ī force acting for a given amount of time will change an object's momentum. An object with momentum can be stopped if a force is applied against it for a given amount of time. As you bring your car to a halt when approaching a stop sign or stoplight, the brakes serve to apply a force to the car for a given amount of time to change the car's momentum. You have also experienced this a multitude of times while driving. In football, the defensive players apply a force for a given amount of time to stop the momentum of the offensive player who has the ball. You have observed this a number of times if you have watched the sport of football. The concepts in the above paragraph should not seem like abstract information to you. As the force acts upon the object for a given amount of time, the object's velocity is changed and hence, the object's momentum is changed. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. The more momentum that an object has, the harder that it is to stop. To stop such an object, it is necessary to apply a force against its motion for a given period of time. Any object with momentum is going to be hard to stop. When a sports announcer says that a team has the momentum they mean that the team is really on the move and is going to be hard to stop. Quantitatively, the effect we are talking about is the change in momentum, Δ p Δ p size 12as previously described, and consider the change in momentum of the first ball that strikes perpendicular to the wall.As mentioned in the previous part of this lesson, momentum is a commonly used term in sports. For example, if the ball were thrown upward, the gravitational force (which is much smaller than the tennis racquet’s force) would eventually reverse the momentum of the ball. A small force could cause the same change in momentum, but it would have to act for a much longer interval of time. In Example 8.1, a very large force acting for a short time had a great effect on the momentum of the tennis ball. The effect of a force on an object depends on how long it acts, as well as how great the force is.
4.B.2.2 The student is able to perform analysis on data presented as a force-time graph and predict the change in momentum of a system.4.B.2.1 The student is able to apply mathematical routines to calculate the change in momentum of a system by analyzing the average force exerted over a certain time on the system.3.D.2.4 The student is able to design a plan for collecting data to investigate the relationship between changes in momentum and the average force exerted on an object over time.3.D.2.3 The student is able to analyze data to characterize the change in momentum of an object from the average force exerted on the object and the interval of time during which the force is exerted.3.D.2.2 The student is able to predict the change in momentum of an object from the average force exerted on the object and the interval of time during which the force is exerted.3.D.2.1 The student is able to justify the selection of routines for the calculation of the relationships between changes in momentum of an object, average force, impulse, and time of interaction.The information presented in this section supports the following AP ® learning objectives and science practices: Calculate average force and impulse given mass, velocity, and time.
Determine the average effective force using graphical representation.Describe effects of impulses in everyday life.By the end of this section, you will be able to do the following:
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