lab6 - IMPULSE AND MOMENTUM Purpose To look at the impulse...

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IMPULSE AND MOMENTUM Purpose To look at the impulse and the change of momentum of a collision and see the effects of using materials to reduce the total impact of the collision. Apparatus Air-track, Air-blower, Photogate, Force sensor, Glider, Balance, Rubber-band, Computer and Data studio program Background The leading cause of death and injury to the youngest third of the population is automobile accidents. Not all collisions cause death. In 1985 4,000,000 injuries were caused by automobile collisions, with only 70,000 leading to permanent brain damage and spinal cord injuries. These injuries to the head and spine often lead to epilepsy, paraplegia and quadriplegia. It is impossible to be able to tell with any certainty the type of injury a person will sustain when in a collision. The type of injuries depend not only on the automobile and its orientation when it collides, but also the configuration of the occupant within the car. The severity of the injury to the occupant also depends upon the size of the force on the occupant during the collision. In order to determine the size of the force within a collision we must look at the ideas of impulse and momentum. This experiment investigates the forces during a collision and examines these ideas by performing an experiment. We understand that when two objects collide they will exert forces on one another. By Newton’s 3rd law the magnitude of the forces are equal but they are in opposite directions. The force exerted on one object may cause it to stop, slow down, or change directions. The result depends upon the size of the force and the length of time the force is applied. For a constant force the product of the force and the time the force is applied to the object is called the impulse, . Eq. 1) ) ( 0 0 t t F Fdt I t t = = The equation indicates that small forces applied over a long time can produce an impulse of the same size as a large force for a short time. For a variable force we can determine the total impulse applied to an object by constructing a graph of force versus time. The total area under the graph will be equal to the total impulse of the object. All objects are said to have momentum and this is quantitatively defined as P = m v E q . 2 ) Here P is the momentum, m is the object’s mass, and v is the object’s velocity. Momentum is a vector quantity and needs to be treated accordingly. When an object experiences an impulse the momentum of the object changes. Δ P = m v after - m v before E q . 3 ) 27
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-0.2 0 0.2 0.4 0.6 0.8 1 1.2 0 0.5 1 1.5 2 2.5 3 3.5 F o r c e , ( N ) Force Vs. Time Tim e (sec.) Figure 1. The graph is of the force versus time. The area under the graph is equal to the total impulse and is equal to 2 N sec. The average force for the 3.1 seconds will be equal to .645 N. Notice that this is smaller then the maximum force felt during the impulse. As we will see in this experiment, the total change in momentum of the object will be equal to the
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This note was uploaded on 08/25/2011 for the course PHYS 164 taught by Professor Johnjames during the Fall '09 term at MO St. Louis.

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lab6 - IMPULSE AND MOMENTUM Purpose To look at the impulse...

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