The springconstant

• Natuurkunde
• Middelbare school
• vmbo lwoo
• Leerjaar 2,3

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You know the difference between elastic and plastic deformation

You know how to calculate the springconstant

You can use a table and draw a graph

Hook's law

Hook's law defines the linear 

relationship between stress 

and strain within the elastic region

Or in other words, it describes the

 relationship between a force at 

work on a spring and the related 

extension of this spring. 

There is a constant relationship between the force at work and

the extension of a sping, as long as the spring can go back to

it's original shape (elastic deformati on).

This relationship is called the springconstant.

Symbols:

F = Force [N]

x = Extension [cm] 

C = The springconstant [N/cm] 

Not every spring is the same, some are more stiff than others.

A stiffer spring will need more force to extend the same amount

of centimeters..its springconstant therefore will be much bigger

than the springconstant of a rather flexible spring.

C=​x​​F​​

Spring constant (C)

F=C⋅X

Formula

Simulation 1

Simulation 2

Simulation 3

1: Stretching a helical spring

What is the relationship between the force used 

to stretch a spring and the subsequent extension?

Set the experiment up as shown in the next slide

1.  Note the position of the bottom of the coil spring.
2. Put one, two, three weights on the spring and note down the number of weights, the force on the spring and the corresponding extension (table)
3. Make a graph of your measurements
4. Option: two identical springs connected serially (or parallel)

number of weights	mass of the weights (g)	force on the spring (N)	extension (cm)
0	0	0	0
1	50
2
3
4
5

Graph

x (cm)

use number of mass pieces

or use Force (N)

m = 50 gram = 0,05 kg

F = m.g = 0,05 kg . 10 N/kg

F = 0, 5 N for one mass piece

So we

1. First research if the theory is correct..
   does the spring react proportionally when you put some weight on it.
   
   
2. Then you can check if a rubber band is reacting the same way.
   
   
3. After that you can connect two springs serially to check what happens then.

1. Write a title
   
2. Write down what you want to research 
3.  Make a table for your data
4. Use your data to make a graph
5. Determine / calculate the springconstant
6. End with your own conclusion using your data and graph about the relationship between the force on a spring and the corresponding extension.

Notebook notes

UPLOAD YOUR GRAPH(s)
for the spring and rubber band
(do make clear what the graphs represent)

1: Building & calibrating a dynamometer

Imagine: a factory that makes measuring instruments is going to launch a new model of dynamometer that allows forces to be measured accurately. A helical spring has been chosen for the new meter. Your job is to complete the design by adding an accurate and easily readable graduated scale.

Purpose

You will be making a graduated scale 

that meets certain requirements. 

requirements

• The range of measurement of the dynamometer must be at least 0 N to 1 N.
• The distance between the marks on the graduated scale must represent no more than 0.1 N. 
• The dynamometer must be at least as accurate as an ‘ordinary’ dynamometer. 

Notebook notes

Explain how you are going to calibrate the dynamometer. 

Make a note of the practical equipment you will need.

Construct the dynamometer and give it a graduated schale

Explain how you carried out the test

Make improvements, adjust your scale if necessary

If you have to write up a report of this experiment, include:

a a photo of the setup, including the calibrated graduated scale;

b how you made the graduated scale;

c the various ways in which you tested the graduated scale;

d your conclusions: how accurate is the dynamometer?