2LA_Lab_6_Newtons2ndLaw6

2LA_Lab_6_Newtons2ndLaw6 - Newtons Second Law(Pre-lab...

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Newton’s Second Law (Pre-lab Assignment included) This week we will make measurements of the relationship between Force and Acceleration, or Newton’s second law, i.e., v F = m v a The lab will consist of two separate sets of measurements: Vary m keeping F constant, and measure a . Measure a on an inclined plane for varying m . Apparatus We will make our measurements on an Air Track to minimize the influence of friction. The basic setup, shown below in Figure 1, consists of an Air Track , rubber bumpers at each end, one glider, one pulley, and two photogate timers. Glider Glider Post Photogates Air Track Bumper Pulley Bumper Figure 1: Air Track Setup for Newton’s 2nd Law Four large weights (about 50 grams each) will be added to the glider to measure a vs. m for fixed F . A 5 gm hanger will provide the force. A string attached to the glider post goes over the pulley and attaches to the hanger (see Figure 2 below). Additional weight may be added to the hanger to increase the force. A balance will be used for mass measurements.
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String Pulley Figure 2: Air Track Pulley with Hanger and Added Mass The Physics Newton’s Second Law F = ma can be tested by applying a known force ( F g = mg from gravity) and measuring the acceleration of the air track's glider. In this experiment there are two masses, m , the mass of the glider, and m h , the hanging mass. Both the hanging mass and the glider are accelerated at the same rate, so the total mass that contributes to the acceleration is ( m + m h ). In the first set of measurements you will use a fixed hanging mass ( m h ), and hence a fixed force( F=m h g ). Mass will be added to the glider, so that F = m h g = (m + m h )a , so that ) ( h m m F a + = with m h constant. This shows that F is propotional to a and the total mass, whereas a is inversely proportional to the total mass. Here F is constant so when a increases, the total mass (m+m h ) decreases. Finally, the air track will be tilted to form a nearly friction free inclined plane. A small aluminum block will be used to raise one end of the air track, creating an inclined plane. The component of the net force acting parallel to the surface of the plane is Hanger Air Track Brass Mass 2
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F = mg sin θ = ma a = g sin independent of the mass of the glider! You will measure this acceleration, compare it to g sin , and verify that the acceleration is independent of the glider mass. Measuring Acceleration We will obtain acceleration ( a ) by measuring the change of velocity with time. The accelerating air track glider will block, in turn, two photogate mechanisms. The lab computer will measure the time that it takes for the glider to pass through each photogate, and the time interval between the gates. These three times are shown schematically as: t 1 t 3 Gate and Pulse (2 gates) The speed of the glider in the first gate ( v 1 ) and in the second gate ( v 2 ) are given by δ t t 2 1 2 v 1 = L t 1 v 2 = L t 3 where L is the length of the glider (which you will need to measure). The acceleration is the rate of change of velocity with time.
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This note was uploaded on 09/30/2009 for the course PHYSIC2LA phy taught by Professor Robertclare during the Spring '09 term at UC Riverside.

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2LA_Lab_6_Newtons2ndLaw6 - Newtons Second Law(Pre-lab...

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