To truly understand the equation, it is important to understand its meaning in words. This equation represents one of two primary principles to be used in the analysis of collisions during this unit.

If both sides of the above equation are multiplied by the quantity t, a new equation results. When combined with the definition of acceleration (a = change in velocity / time), the following equalities result. a) stated that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object.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. As mentioned in the previous part of this lesson, momentum is a commonly used term in sports.

Impulsive force model impulse