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1. A student finds the following values from a graph between M and x in the stat

ID: 2040545 • Letter: 1

Question

1. A student finds the following values from a graph between M and x in the static method of determining the spring constant k: x1 = 0.5 cm, x2 = 7.8 cm; M1 = 120 gm; M2 = 300 gm. Calculate the value of k. 2. Consider the following data for an experiment to study the spring constant by dynamic method: Number of oscillations, N 25 Load M1 120 gm, average time for N oscillations 11.0 seconds Load M2 280 gm; average time for N oscillations 16.9 seconds Calculate the spring constant k (Note that the mass of the hanger is not given.)

Explanation / Answer

Q1.

equation of straight line can be given as:

(M-120)/(x-0.5)=(300-120)/(7.8-0.5)=24.658

==>M=120+24.658*(x-0.5)

==>M=107.67+24.658*x

slope=24.658 gram/cm=2.4658 kg/m

but as we know, slope for this graph will be k/g.

hence k/g=2.4658

==>k=2.4658*g

=2.4658*9.8

=24.165 N/m

Q2.

for dynamic method, graph of T^2 vs mass is taken

where T=time period

slope of this graph is given by 4*pi^2/k

where k=spring constant

from the given data, slope of T^2 vs mass line:

(T1^2-T2^2)/(M1-M2)

where T1=11/25=0.44 seconds

T2=16.9/25=0.676 seconds

then slope=1.6461

==>4*pi^2/k=1.6461

==>k=23.983 N/m