Measure the distances to the nearest millimeter and then estimate to the nearest tenth of a millimeter. These distance measurements are critical since they are multiplied by a large number in calculating the acceleration. This procedure improves the accuracy of the set of measurements. Please note that the distance to be measured is the total distance to each dot from the starting point (zero) and not the distance from the preceding dot. Label this dot zero (0) and measure the distance from this zero point to each successive dot, measuring as many as possible (at least a dozen). Find a dot for a starting point by dropping down at least a centimeter from the first marks so that the falling object will have cleared the magnetic field influence. If a dot is missing, you need to take that into account in entering your data into the calculation program described below.ģ. You should be able to detect a "misfire" of the apparatus if a dot is missing or if there is an extra mark. Look at the dots on the tape and note the way the distance between dots increases. Secure the ends of the tape to the table with masking tape.Ģ. (A demonstration will be conducted so that you can see how the tape was made.)ġ. You will be provided with a tape from the free-fall apparatus. Since the object is accelerating, the distance between marks should increase. With 60 sparks per second, the space between successive marks represents the distance that the object has fallen in 1/60 second. The passage of the spark through the waxed tape leaves a small mark or spot on the tape, marking the position of the falling object. A sparking device of known frequency (60 Hz) passes each spark from an outer wire through a conducting metal ring on the object, through a waxed recording tape, and on to a second wire to complete the circuit. When the switch to the coils of the electromagnet is opened, the magnet can no longer hold the object, and it falls freely into a cup below. The free-fall apparatus has an electromagnet to hold the object until the record of its fall is to be made. In this experiment the acceleration of gravity, g, will be determined directly from the motion of a freely falling object using equations 3 and 4. Where v2 and v1 are the average velocities over any two successive time intervals t. If equal time intervals t are used then the acceleration can be expressed as If the object accelerates uniformly as a result of the application of a constant force such as gravity, the acceleration can be found as the rate of change of the velocities over successive intervals of time. Where s is the distance traveled in time t and vavg is the average velocity for the time interval t. One way to describe the motion of an object is with the relationship For relatively small, smooth objects of considerable density, however, the error introduced by conducting such experiments in the atmosphere is quite small.įor the description of the motion of an object, the variables distance, velocity, acceleration and time are involved. Strictly speaking, free-fall experiments must be conducted in a vacuum so that the force of air resistance does not affect the results. Is the same for all objects and is known as the gravitational acceleration "g". Galileo is credited with discovering that the force of gravity is the cause of weight and that all bodies, regardless of their mass, are accelerated by the force of gravity at the same rate. Where F represents force, a is the acceleration, and m is the mass of the object.Īristotle and other ancient philosophers reasoned (mistakenly) that the heavier a body is, the faster it should fall. Freefall Uniformly Accelerated Motion The Freely Falling ObjectĪn object that is acted upon by a force which is constant in magnitude and direction will be accelerated with constant acceleration in the direction of the force.
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