In much the same way knocking balls in pool against one another transfers energy from one ball to the next, objects that collide with one another transfer momentum.
According to the law of conservation of momentum, the total momentum of a system is conserved. You can create a total momentum formula as the sum of the momenta for the objects before the collision, and set this as equal to the total momentum of the objects after the collision. This approach can be used to solve most problems in physics involving collisions. When dealing with conservation of momentum problems, you consider the initial and final states of each of the objects in the system.
The initial state describes the states of the objects just before the collision occurs, and the final state, right after the collision. After studying physics and philosophy as an undergraduate at Indiana University-Bloomington, he worked as a scientist at the National Institutes of Health for two years.
He primarily performs research in and write about neuroscience and philosophy, however, his interests span ethics, policy, and other areas relevant to science.
How to Calculate Momentum. Momentum, therefore, increases with increasing speed as well as increasing mass. This situation fits logically, then, with the definition of momentum in physics. The momentum p of an object of mass m and velocity v is defined according to the following relationship:. Notice that momentum, like velocity, is a vector with both magnitude and direction. As the mass or velocity of an object increase, so does the momentum. Recall that acceleration is simply the time rate of change of velocity.
Thus on average , we can write the following:. Note that because m v appears in the net force expression, we can write it in terms of momentum p. The net force on an object is therefore the time rate of change of its momentum. Practice Problem : A kilogram object is moving at a speed of 10 meters per second. What is its momentum? Because no direction is specified, we are only interested in determining the magnitude of p, or p.
Let's now consider some arbitrary number of objects; the total momentum P of the system of objects is simply the sum of all the individual momenta:. In the same manner, following Newton's second law, we'll call F tot the sum of all the forces acting on the objects. But this sum, F tot , is simply the sum of all external forces acting on the system of objects. In other words, the time rate of change of the total momentum of the system of objects is zero in this case; this is simply a statement of the law of conservation of linear momentum for a closed and isolated system.
That is to say, the total momentum is constant for a given system of objects on which no external force acts. This conclusion is extremely useful for problems involving, for instance, collisions of objects.
The following practice problems allow you to explore the implications of this result. Practice Problem : A projectile of mass 1 kilogram traveling at 80 meters per second collides head on with another projectile of mass 2 kilograms traveling at 60 meters per second in the opposite direction.
If the projectiles "stick" together after their collision, what is their velocity after colliding? Solution : Let's draw a diagram of the situation before and after the collision. We also define the direction x for reference.
From the lesson we learned that the total linear momentum of a system of objects must be conserved that is, unchanged if no external forces act on that system. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion on the move then it has momentum. Momentum can be defined as "mass in motion.
The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.
In physics, the symbol for the quantity momentum is the lower case p. Thus, the above equation can be rewritten as. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity. The units for momentum would be mass units times velocity units. In each of these examples, a mass unit is multiplied by a velocity unit to provide a momentum unit. This is consistent with the equation for momentum.
Momentum is a vector quantity.
0コメント