MARCH 03, 2010

Great ... thanks Dave.

Okay, so today we went over the front page of Chapter 9 Study Guide. Here are the answers if you missed any ...

9.1 IMPULSE AND CHANGE IN MOMENTUM
Momentum and Impulse
The amount of force needed to change the motion of a moving object depends on the velocity and mass of the object. The momentum of a body is the product of the body’s velocity and mass. Momentum is a(n) vector quantity. Its direction is the same as the direction of the velocity. The equation used to calculate momentum is p = mv. In this equation, p stands for momentum, m stands for mass, and v stands for velocity. The unit for momentum is the kilograms meters/second. The product of the force applied to an object and the time interval over which it acts is called the impulse. The direction of the impulse is the same as the direction of the force that is applied. The unit for impulse is the Newton • second. The impulse given to an object is equal to the change in the object’s momentum. This equality is the impulse-momentum theorem. It is also another statement of Newton’s second law of motion.

We were also suppose to finish the back of Chapter 9 Study Guide today, here are the answers …

9.2 THE CONSERVATION OF MOMENTUM
Newton’s Third Law and Momentum
If one object collides with another, the momentum of each object changes. The first object exerts a(n) force on the second object, and the second object exerts a(n) force or equal magnitude and opposite direction on the first object. If objects neither leave nor enter a system, the system is described as closed. If no external forces act on a system, the system is described as isolated. When there is a collision within such a system, the net change in momentum is zero. The total momentum before the collision is the same as the total momentum after the collision.
Law of Conservation of Momentum
In a closed, isolated system, the momentum does not change. This statement is the law of Conservation of Momentum. When two objects within the system collide, the magnitude of the momentum lost by one of the objects is equal the momentum gained by the other object. Momentum can be transferred from one object in the system to another.
Internal and External Forces
Internal forces act between objects in a closed system. External forces are exerted by objects outside the system. The total momentum of a system is conserved only when there are no external forces acting on the system.
Conservation of Momentum in Two Dimensions
The law of conservation of momentum does not depend on the direction in which objects move before and after colliding. The momentum of two objects in a system can be represented by two vectors, which can be resolved into vertical and horizontal components. After all vectors are added, the final sum must equal the original momentum of the system.

We also did questions from the textbook on Page 173, # 1 - 4. Here are the answers.

Okay next scribber is Kasey La :)