I aim to find out if the mass of an object affects the speed at which it falls.

According to  Galileo demonstrated his conclusions by dropping weights from the leaning tower of Pisa."

I will drop the object, which will be a small container, from a height of 30cm. I will measure the speed of the object using a light gate, which will make my results accurate to two decimal places. I will use sand to increase the mass of my object because this will be very accurate and it will not alter the shape of the object.

After my preliminary test I concluded that 30cm would be the best height to drop the container from. To start with I tried 0.5m, 1m, and 2m. These all gave the same results and I knew the terminal velocity should be higher and as the object is in the air for longer each time, they should not have the same speed. I then tried throwing the container through. This again gave the same result. This was because the light gate could not measure faster than 2.59m/s with an object of 3cm. I then lowered my height to 30cm. The speed was lower than 2.59m/s, so I used this height.

To keep this a fair test I will,

• Keep the object shape the same. If I did not keep the shape the same I would be measuring the affects of air resistance as well.
• Keep the height that I drop the object from the same.
• Keep the object which I am dropping the same.

All I will change is the mass of the object

 

This is a diagram of my experiment.

As you can see I have taken three sets of results for each mass and used the average, to make my results accurate.

Analysis

My results have proved my prediction, that the mass would not affect the speed. This is made clear by this scatter graph, with a line of best fit.

To prove that my results are accurate I can use the formula mass x gravitational pull x height (MGH) to calculate the amount of kinetic energy gained/the amount of potential energy lost.

When something falls, the potential energy it has is converted into kinetic energy. This is why when an object falls further it falls faster.

   m    x  g  x   d     = Potential energy lost

0.01g x 10 x 0.3m = 0.03J

Using this I can find out the velocity that the object should fall at without air resistance. Some of the potential energy will have been lost due to heat caused by air resistance.

0.03J = ½mv²

0.03J = ½ x 0.01g x v²

v² = 0.03 / 0.005

v= √6

v = 2.4494897 m/s

As this velocity is without air resistance and my experiment's results take into account air resistance, it is a reasonable assumption that my results are accurate.

 2.4494897 - 2.1855556 = 0.2639341m/s

As you can see 0.2639341m/s is very little difference. The air resistance was so little because the object was not falling very far

Evaluation

This experiment was successful as it proved my prediction that the mass of an object does not affect the speed at which it falls.

I could have made the experiment more accurate by using a system to drop the object rather then myself as sometimes the object spun in the air, so the results were inaccurate as not the whole 3 cm of the object broke the beam. I tried to combat this by doing the experiment three times each mass. If I had increased the amount of times I had done the experiment I could have made the results even more accurate.

If I used a mechanism to drop the object this would help eliminate spinning. However, the sand was sometimes uneven inside the container so this would make the object spin at the start. The other problem with spinning was that the object would have fallen faster when it spun because it would have less air resistance. It would have been more accurate if I had used weights of the same size but different mass, instead of sand.

Also, when I dropped the container, I may have not dropped it from exactly the same distance every time. I also may have added force to the object with force when I dropped it. The mechanism would have also stopped this.

This would be a diagram of the mechanism I would use if I were to do it again.

When I pull the string, the mechanism would drop the object evenly.

Even with all these minor problems my results are still very accurate.

I now know for a fact that my prediction is correct because I have proved it in 3 different ways,

• Using a practical test (experiment)
• Using theoretical calculations (The formulas)

• Using other people results as well as my own.