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# Controll experiment

Now I will use these values and try to make a graph of it with velocity against mass. The graphs show the best straight-line gradient, the max gradient is and the min gradient is. The range of gradient is: Half the range of gradient, I find the uncertainty in the best straight line , which means a gradient with an uncertainty of The uncertainty dividing with the gradient, multiply that value with 100 I get a percentage error of about 105%, and this is not reasonable at all.

So, I will evaluate this large uncertainty in my evaluation at the end and continue adjusting my graph to get an offset point for both velocity and mass to be 0(origin). I tried different regression on my calculator and found the logarithm regression having an offset closest to 0(origin).

This graph looks not good. It has a correlation of 0.512 which is really bad. Maybe it has something to do with my huge uncertainty calculated earlier. So I don’t know if I have a good result.

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Let me evaluate and conclude it in my conclusion. Conclusion and evaluation To evaluate my result I have to look into the uncertainty and the result. The uncertainty I found was 105% which is very suspicious. It should not be possible, so there has to be reason for this error. My idea proposed that mass and velocity is proportional to each other. However, my result did not show that proposal. Maybe I should have tried another ball instead of a light ping pong ball of 3 g.

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This may have influenced the error.

So neglecting my large uncertainty, I found the logarithmic graph to show the best model of the relationship between velocity and mass. Which means my idea of mass and velocity to be proportional is wrong. To improve my experiment, I could have tried to use more balls with different masses to get a wider data. Maybe I should have measured the velocity of the ball after it bounces and also using a mechanical release to drop the ball.

## The distance between an object and a light source

In this investigation, a controlled experiment will be conducted to determine whether the distance between an object and a light source has an effect on the intensity of light and if so, do the illuminance increase or decrease as the distance from the light source increases. Research will be formulated by conducting a controlled experiment in which we will observe the intensity of light received by a light sensor at various distances and evaluate the results gathered to determine the relationship between light intensity and distance. This phenomenon can be experienced when an oncoming car has it head lights switched on, the light intensity seems to increase as the car approaches.

Similarly, the rate of photosynthesis also relies heavily on the intensity of light, as the process is seemed to be quicker when the sun’s light intensity is strong. Thus, the relationship between light intensity and distance is important to investigate so that experimental reasoning can be deducted for these phenomena’s. The intensity of the light is the amount of light that falls on a specific object. This measure is called illuminations and is expressed in Lux when the distance is measured in metric terms. A lux equals one lumen per square metre. (Anderson, 2009)

## Hypothesis

Increasing the distance of the light sensor from the light source will decrease the intensity of light (or luminance) detected by the sensor. This hypothesis is based on the knowledge that as light waves travel out from a light source in straight lines, they spread out and become less concentrated as they travel further away- making it appear dimmer. Furthermore, when an object is placed near a source, majority of the light waves emitted are concentrated on it, however when placed further back, only a small proportion of the waves are hitting it. Due to this, increasing distance ultimately decreases the illuminance (how much light from a source hits a specific object) and thus, the light intensity.

## Variables

### The independent variable (the variable being changed):

The independent variable is going to be the distance between the light sensor and the light source (cm) with measurements varying from 10cm-100cm and increasing at 10cm increments. We will do this in order to see the effects varying distance has on light intensity. The variable will be altered by increasing the distance between the two objects by 10cm (interval length) for each set of trials. We will measure and change this gap by using a metre ruler to determine the exact distance and then we will place the light source at one end and the sensor at the determined mark on the ruler.

### The dependent variable (the variable being measured):

The dependent variable is going to be the intensity of light illuminated by the light source at each particular distance (ranging from 10cm-100cm). This variable will be measured in the unit of measurement LUX. To determine the LUX illuminated at various distances, we will use Data Studio to give us accurate measurements of light hitting the light sensor that will be located at one of the ten distances, thus giving us our measurement for the particular trial.

### The control variables (the variables kept the same):

The other variables, which we need to keep constant, are:  The same conditions present around the experiment (room temperature, background light, disturbance, etc.). To ensure that the experiment is fair, we will minimize any background disturbance by conducting the experiment in a secluded area away from other groups. We will also close all blinds and switch off the room light so that there is little to no background light interfering with the light sensor’s readings. This is essential for the data’s reliability as background light can affect the readings by increasing the light intensity (lux) picked up by the sensor- more than what is being emitted by the light bulb.