PH1004_Experiment_2 - PH1004 Exp 2: Forces PH 1004...

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PH1004 Exp 2: Forces 1 PH 1004 Laboratory Instructions Experiment 2 Forces Background Newton’s first law states that an object at rest remains at rest unless acted upon by an outside force, and an object in motion continues to travel at constant velocity unless acted upon by an outside force. This law is also referred to as the law of inertia. Newton’s second law deals with force. Force can be defined as an external influence (sometimes described as a push or a pull) on an object that causes it to accelerate relative to an inertial frame of reference. The direction of the force is the same as the direction of the acceleration, assuming that there are no other forces acting on the object. The magnitude of the force is equal to the acceleration of the object times its mass. Thus, mass is a measure of an object’s inertia, or resistance to acceleration. Experimentally it is observed that forces add as vectors, and therefore, all the forces on an object act together like one net force. Newton’s Second Law can then be written as = = a m F F net r r r . (2-1) In this experiment, we use measurements for the acceleration of the glider to calculate the acceleration due to gravity, g . As in Experiment 1, an air track will be used. In Part A of this experiment, the force on the glider is again exerted by a string, which is connected to the glider, draped over a pulley, and attached to the hanging mass. In Part B, one end of the air track will be raised so that the glider will accelerate toward the other end. In this way, the force that causes acceleration is a component of the gravity force. Apparatus Required equipment: 1. An air track assembly including air supply pump, and other accessories.
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Exp 2: Forces 2 2. A glider with a flag. 3. Two photogates, labeled G1 and G2. 4. Hanging weights. 5. A string (to attach the glider to a weight via a pulley). 6. Lab-jack (for raising one end of the air track). 7. A data acquisition box and a computer. Part A. Pulling Force A pulling force will be applied to the glider on the air track using a string passed over a pulley and a hanging mass. The relationship between the glider’s acceleration a and the gravitational acceleration g is given by g m m m a gl + = (2-2) where m is the mass of the hanging weight, and m gl is the mass of the glider. Equations 2-3 that represent Newton’s Second Law for the horizontal and vertical components of the net forces acting on the glider and hanging mass respectively, explain how equation 2-2 is derived: a m m mg ma T mg a m T gl gl ) ( + = = = (2-3) Note from equation 2-2 that glider acceleration, a , is expected to be a linear function of the ratio gl m m m + , with zero intercept: Based on equation 2-2 we develop the following method for determining the acceleration due to gravity g : Accelerations of the glider, a , are found for several values of the hanging mass, m . m
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PH1004_Experiment_2 - PH1004 Exp 2: Forces PH 1004...

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