Teaching Physics with the Physics Suite

Edward F. Redish

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Comparing mass-spring and pendulum: 2

Below is shown the graph of the x position measured by a sonic ranger but the origin is shifted so that the 0 of the coordinate occurs at the equilibrium point of the system.

A. Assume that the graph represents the position of a wooden disk hanging on a spring from a bar and that x is the up-down coordinate with + being up.

A1. The mass of the disk is 500 g. Find the spring constant, k.

A2. How much will the spring be stretched when the mass is at the equilibrium point?

B. Now assume that the graph represents the left-right position of a pendulum and that x is positive to the right as shown.

B1. The mass of the bob is 150 g. Find the length of the pendulum, L.

B2. Could you use the information in the graph to figure out the maximum angle the bob will reach? If so, explain briefly how. If not, explain why not.

Page last modified Janaury 27, 2011: O51