Callipers are used to measure the dimensions of objects with high precision and are often used in laboratories. Here you can learn how to use Vernier callipers to measure the widths of different samples.

Measurement is the starting point of meaningful scientific understanding. Callipers are common pieces of equipment used across science and engineering that allow object dimensions to be measured with a high degree of accuracy and precision. This can be vital for designing mechanical components or for experiments in which sample dimensions affect the outcomes, e.g. resistance or stress.

The following quick instructions are also in the downloadable file below:

- Drag moveable part of lower jaw to make jaw separation larger than sample width.
- Drag sample into lower jaws. Sample will snap into place.
- Drag moveable jaw blade to close jaws around sample.
- Read width from scale (see below for how to do this).
- Type width into ‘Sample Width’ text box and click ‘Check’ to see if you were right (green = correct, red = incorrect).
- Drag a sample out of the jaws (or press ‘Reset’) to return it to its original place and select a new sample.
- Click ‘New’ for a new set of samples with different widths.

To read the caliper scale (see full instructions for more details):

- Find the tick mark on the main scale (upper scale) that is just below the ‘zero’mark on the Vernier scale (lower scale). This gives a whole number of millimetres for sample width.
- Locate the tick mark on the Vernier scale that is most closely aligned with any tick mark on the main scale. This gives the number of tenths of a millimetre in the sample width.
- Add the values from the above steps to find the overall sample width.

Download the file below to view the full instructions for the Callipers experiment.

- Measure the width of ten samples. Check to see how many you measure correctly and give yourself a mark out of ten. Repeat this until you get 10/10 every time!
*Error analysis:*- Measure and record the width of ten or more samples.
- Use the width data to calculate the cross-sectional area of each sample.
- Determine the
*absolute error*and*fractional error*for each width measurement. - Determine the
*absolute error*and*fractional error*for each cross-sectional area value. *Statistical analysis:*- Measure and record the width of ten or more samples.
- Calculate the mean and standard deviation of the width measurements.
- (Advanced experiment) Calculate the
*standard error*of the width measurements and from this determine the confidence level of the mean.

Micrometers are used to measure the dimensions of objects with high precision. They are commonly used in laboratories. Here you can learn how to use micrometers to measure the widths of different samples.

Measurement is the starting point of meaningful scientific understanding. Micrometers are common pieces of equipment used across science and engineering that allow object dimensions to be measured with a high degree of accuracy and precision. This can be vital for designing mechanical components or for experiments in which sample dimensions affect the outcomes, e.g. resistance or stress.

The following quick instructions are also in the downloadable file below:

- Drag the
*ratchet screw*(right hand end) sideways to open or close the micrometer (the anvil part) in large steps (note that real

equipment doesn’t include this). - Click on the
*rotating**scale*and drag up or down to open or close the micrometer in small steps. - Open the micrometer and drag a sample into the anvil gap. The sample will snap into place.

- Close the micrometer around the sample. Make sure to follow use of the ratchet screw with the rotating scale to close the micrometer.
- Read width from scale (see below for how to do this).
- Type width into the appropriate text box and click ‘Check’ to see if you were right (green = correct, red = incorrect).
- Drag a sample out of the jaws (or press ‘Reset’) to return it to its original place and select a new sample.

You can also click ‘New’ for a fresh set of samples with different widths.

To read the micrometer scale (see full instructions for more details):

- Find the largest valued tick mark on the main scale that is revealed from behind the rotating thumbscrew. This gives a whole number of millimetres for sample width.
- Locate the tick mark on the rotating scale that is most closely aligned with the main scale axis. This gives the number of tenths of a millimetre in the sample width.
- Add the values from the above steps to find the overall sample width.

Download the file below to view the full instructions for the Micrometer experiment.

- Measure the diameter of ten ball bearing samples. Check to see how many you measure correctly and give yourself a mark out of ten. Repeat this until you get 10/10 every time!
*Error analysis:*- Measure and record the diameter of ten or more ball bearing samples.
- Use the width data to calculate the volume of each sphere.
- Determine the
*absolute error*and*fractional error*for each diameter measurement. - Determine the
*absolute error*and*fractional error*for each volume value. *Statistical analysis:*- Measure and record the diameter of ten or more ball bearing samples.
- Calculate the mean and standard deviation of the diameter measurements.
- (Advanced experiment) Calculate the
*standard error*of the diameter measurements and from this determine the confidence level of the mean.

Structural materials are required to withstand a variety of applied loads in use. Understanding how these materials respond to applied loads is vital for informed materials selection. Here you can investigate how materials behave under tensile loading (loads applied along the length of a material to cause stretching).

Press GO to launch the experiment!

*What is ‘Tensile Testing’?*

The ‘tensile’ properties of a material describe its most basic mechanical behaviour – how much does a material stretch when it is pulled and how much of the stretching is permanent? ‘Tensile Testing’ is the process of measuring a material’s tensile properties.

*Why are tensile properties important?*

Understanding of tensile properties is vital for any application that uses materials structurally, i.e. to withstand or apply force. The range of uses this covers is enormous. **Strong** and **stiff** structures are used in vehicles (cycles, cars, trains, aeroplanes, spacecraft), bridges and buildings, sports equipment and bio-implants (e.g. hip joint replacements). **Flexible **materials are also used in many of these applications. **Thin **but **robust** materials are used in touchscreens. **Hard** materials are used in machines and robots that process and shape other materials and as durable coatings that improve the performance and lifetime of aerospace and bio-implant components. **Elastic** materials can be stretched enormously before any permanent change is made and are used in springs and high performance fabrics. And it’s not just how a component is used – many manufacturing processes involve changing a component’s shape or response to applied forces, e.g. **extrusion** to make tubes, beams and bottles; **drawing** to make springs or wires; or **forging** and **rolling** to shape and harden metals.

* *

To select a sample:

- Click the lower sample holder to go to the sample view.

- Open the calliper jaws, drag a sample of choice between the jaw and close the jaws around it.

- Use the Vernier scale to measure the sample width.

- Use the Sample Width textbox and Check button to verify measured width values.

- Use the Reset and New buttons to control the samples you are considering.

- Click the number region of a sample held in the callipers to use it in the tensile testing machine.

To set the strain increment:

- Click the Set button (display starts to flash)

- Use the keypad and the Del button to enter the desired Step value

- Click the Set button again (display stops flashing)

To apply strain to samples:

- Set the strain increment value as described above.

- Click the up arrow to increase the applied strain by the Step increment value.

- Click the down arrow to decrease the applied strain by the Step increment value.

- Measure (and record) the applied load (force) using the needles on the Load dial.

- Turn off the strain control unit and click on the lower sample holder to select a new sample.

These instructions can be downloaded below.

Download the file below for the full instructions, including background, relevance, operating instructions and questions.

Structural materials are required to withstand a variety of applied loads in use. Understanding how these materials respond to the applied loads is vital for informed materials selection. Here we investigate how materials behave under *tensile loading *(loads applied along the length of a material to cause stretching).

The Tensile Test experiment allows a number of mechanical tests to be performed on materials, including:

- Determination of full stress-strain curve to fracture, using either ‘engineering’ or ‘true’ value
- Observation of elastic behaviour and calculation of Young’s modulus
- Observation of the onset of plastic behaviour and permanent deformation
- Calculation of moduli of resilience and toughness
- Calculation of strain energy in a system
- Calculation of work done in deforming a sample

The Tensile Testing experiment can be used for a wide range of investigations.

This downloadable pdf below contains a range of example short and long questions.

We have also provided a spreadsheet file to allow you to enter your SAMPLE WIDTH, STRAIN and APPLIED LOAD data and obtain stress-strain plots. (HINT: to investigate the general form of stress-strain curves with younger students, use a default sample width of, say, 7 mm)

Watch the video above and download the file below to learn about the scientific background of Tensile Tests