# Ruler and Steel Ball Essay

Submitted By cheesusan
Words: 1916
Pages: 8

Introduction
The purpose of this design lab is to assess the size of impact craters of a steel ball on flour when dropped from a specific height. A steel ball is dropped at various heights over a bowl of flour. When the ball hits the flour, a crater is formed. What I am trying to investigate is the correlation between the height (x) at which the steel ball is dropped and the diameter (y) of the crater.
Research Question
How does the diameter of the crater depend on the height at which the ball is dropped at?
Independent Variable: The height at which the steel ball is dropped at.
Dependent Variable: The diameter of the crater.
Controlled Variables:
The mass of the steel ball (70.0 g)
The width of the steel ball (2.4 cm)
The initial velocity of the steel ball
Acceleration due to gravity
The amount of flour that ball is being dropped onto
Method
controlling the variables

To measure and set the height at which the ball is to fall, I used a measuring tape. In this situation, it is favourable to use a measuring tape over a ruler since a ruler has a finite length, which means I have to manipulate the ruler, for example, dig it into the flour, in order to get an accurate length. A tape measure is better in this case as I can set the desired length and put it on the surface of the flour, rather than digging it in and compromising my results. I positioned the bottom (the hook end) of the tape measure on the surface of the flour, not submersed, and measured the desired length I wished to drop the ball at.
I decided that using the hook end at the bottom as my starting point would be efficient, as it is the most logical idea and it serves more convenience. It is convenient because it leaves more area for the steel ball to drop on.
The ball is then aligned with the end of the tape measure to set the specified height. To reduce error due to parallax, I positioned my head parallel to the ball, ensuring that it met the drop height requirements. The ball is then dropped onto the flour.
The crater the ball creates is measured. I measured the crater with the ball still in the flower since taking it out would compromise the crater shape and accuracy of the measurement. I try to keep my breathing to a minimum as and excessive breath may blow flour into or outward from the crater, skewing the measurement.
Controlling the controlled variables The same ball and volume of flour was used throughout the experiment. After each trial, I smoothen out the surface of the flour to be able to reproduce accurate results. I ensured the steel ball’s drop height by putting it side by side with the end of the tape measure and dropping it from there. The experiment was conducted on Earth to ensure that acceleration due to gravity was constant. The initial velocity of the ball is ensured by me dropping the ball, not adding any extra force to the ball as it is released.
Hypothesis
I believe that the diameter of the crater will be directly proportional to the distance at which the object is dropped at. I believe this because acceleration due to gravity is constant so there would not be any fluctuations in velocity.
Collecting Data
The experiment was repeated 3 times each for each of the different heights. The heights ranged from 20 cm to 100 cm, 0 cm being the control. The classroom rulers posed many inconveniences so I decided to use a tape measure instead. I ran some tests on what the idea ball would be for my experiment would be. I tried the marbles in classroom, but the craters were too small, being troublesome to measure and hard to get accurate. I decided to use the heavier, bigger steel ball since it could create big enough craters easy enough for me to measure.
The bottom of the steel ball was aligned with the desired height.

Results
Raw Data Table
A table of the data accumulated from the 3 repetitions for each of the 6 different heights is presented below.
Uncertainty in distance is estimated to be approximately ½ of the smallest increment of the…