# Using a set square to reduce parallax error

• MBBphys
In summary, when conducting an experiment to calculate the acceleration of free fall using the electromagnet and trap door arrangement, the biggest error lies in the measurement of the height over which the ball falls. To reduce this error, the use of a set square is recommended to ensure that the eye is level with the ruler, thus minimizing the potential for parallax error. This can be achieved by making sure that the line between the eye, the object, and the ruler is at a 90 degree angle.

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## Homework Statement

In one of my revision guides, there is an experiment for calculating the acceleration of free fall using the electromagnet and trap door arrangement. The biggest error is in the measurement of the height over which the ball falls. The guide says: "You could reduce the error in your measurement of h by using a set square to make sure your eye is level with the ruler".
What does that mean? How do you do that?
Thanks!

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## The Attempt at a Solution

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Maybe this?

https://en.wikipedia.org/wiki/Set_square

By the way, I'm not familiar with this experiment using an electromagnet and trap door, the way you described it. So I'm not sure how the "set square" fits in. You might want to be more specific about the experimental details; perhaps post the entire question verbatim.

Parallax error occurs when the line between your eye the object and the ruler isn't 90 degrees to the ruler.

I would normally insert a diagram to explain but unfortunately I'm stuck with this tablet for a few days.

## 1. What is a set square?

A set square is a tool used in geometry and technical drawing to create or measure angles. It is typically made of transparent plastic or metal and has two arms of different lengths with marked degree angles on each side.

## 2. How does using a set square help reduce parallax error?

Parallax error occurs when the object being measured is not directly aligned with the measuring device, causing the measurement to be inaccurate. By using a set square, the object can be placed directly against one of the arms, eliminating the possibility of parallax error.

## 3. Can a set square be used to measure all angles?

No, a set square can only measure angles that are either 90 degrees or smaller. For larger angles, a protractor or other measuring tool would be needed.

## 4. How do I use a set square to measure an angle?

To use a set square, place one of the arms against the side of the angle you want to measure. Then, align the other arm with the other side of the angle. The degree markings on the set square will indicate the measurement of the angle.

## 5. Are there any precautions to take when using a set square?

Yes, it is important to ensure that the set square is clean and that there are no scratches or marks on the surface, as this can affect the accuracy of the measurement. It is also important to handle the set square carefully to avoid damaging or bending the arms.