Measuring Mass Purpose To use a simulation with simple springs to determine the

Question

Measuring Mass Purpose To use a simulation with simple springs to determine the mass of an unknown object Open the PhET simulation, "Masses and Springs. spring-lab). When the simulation opens, the screen should resemble this image Althe springs are identical, but you can adjust the stffiess of spring 3 for greater or lower sensitivity. For this investigation you will only use spring 1. The goal of this investigations is to detemine a value for he mass of the unknown cylinders (green gold, and red). All you have to work with is a spring, a few known mas standards, and a centimeter ruler. You can move the Hang Me masses and the ruler using the dlick& drag method. Once you are familiar with the behavior of the spring simulation, devise a method to determine the mass of the unknown cylinde describe below. It should be clear from your witten descripton how your method wil produce a mass value for the red cylinder Procedure Defend: Explain why you think your procedure wll leld a vald measurement for the mass of the cylinders

Explanation / Answer

1. procedure to know unknown mass

hang the known masses and note down the dosplacement of the spring form the mean position

m1 = 0.1 kg, dx1 = (40 - 30)/100 = 0.1 m, spring constant k = m1g/x1 = 0.1*9.81/0.1 = 9.81 N/m

do this with other known masses

m2 = 0.25 kg, dx2 =(56-30)/100 = 0.26m , spring constant k = m2g/dx2 = 9.8 N/m

hence spring constant k = 9.81 N/m

so now hang unknown mass and read its displacement on the spring

m = ?

dx = 30 cm = 0.3 m

hence m = kx/g = 9.81*0.3/9.81 = 0.3 kg

2. this procedure will yield a valid measurement of mass as mg = kx is valid for springs wheen they obey hookes law, and under this assumption the resultant of the displacement will give us the unknown mass once we know the spring conjstant

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