Falling ball (María M, Kristina P, Victor S, Alvaro P)

Falling ball experiment

- Research question: Investigation on how changing the height of a falling ball affects the surface it hits.

- Objective: To investigate how the depth of the marble in the polyacrylate solution changes when there is a change in the vertical height of the free fall, by measuring the distance from the top of the polyacrylate to the bottom of where the marble has sunk.

- Data:

This table shows the results:

Height (cm)	Depth (cm)					Average (cm)
25	1,5	1	1,5	2	1,25	1,45
50	2,5	2	3	2,25	2,5	2,45
100	4	4,5	4,5	5	4,25	4,45
150	5,5	4,5	5	6	5	5,2

Sodium polyacrylate: 5 grams in 250 mL water. 

- Hypothesis: 

Our hypothesis states that when we throw a marble into the Al3B5 solution the height (h)  from which we throw it, will affect the depth of the hole that the marble makes in the solution. Due to gravity, when the marble is thrown from a certain height it will sink into the solution a certain amount. The higher the marble's starting position is, the deeper it will sink, which means that the height of the marble is directly proportional to the depth. For example, we expect that if we throw the marble from 50cm from the solution, it will sink less than when we throw it from 150cm.

There is also a relationship between the height of which the marble is dropped and the energy it releases (kinetic). When the marble is dropped futher away from the solution, the kinetic energy released is bigger. This happens because the higher the marble's starting postion is, the more gravitational energy it has (law of gravity, the gravity pulls the object with a stronger force, increasing it's energy).

KE = 0.5 • m • v2

m = mass of object

v = speed of object

g=9,8m/s2

PE (gravitational) = weight x height

weight= mass x g

- Variables:

Independent: This is the height of the free falling ball  (25, 50, 100, 150, 200 cm), because it's the one which we change. The height was measured using a ruler for the first two numbers (25cm and 50cm), and then a tape measure for the rest.

Dependent: The dependent variable is the depth(cm) of the marble in the polyacrylate, because it's the one which changes depending on the height. This is measured accurately with a ruler, from the top of the solution in the beaker, to the bottom of the marble.

 Controlled: The temperature (Cº), pressure (atm)… Because they are maintained constant. They don't change in the whole experiment. 

  - Method: 

Materials.
Solution
5 marbles
Ruler
Tape Measure
Table
Pencil
Beaker

1. Prepare the solution. Put 5 grams of polyacrylate into a beaker, and add 250 mL of water. Mix until the solution has a jelly-like consistency.

2. Prepare the marbles. Pick out 5 marbles which have the same size and weight.

3. Measure out the distance. Using a ruler or a tape measure the distance. Then, hold the marble at the chosen height.

4. Drop the marble. You must drop the marble 5 times at a given height, and measure the depth from the top of the solution in the beaker to the bottom of the marble.

5. Repeat step 3 and 4 with all the heights chosen.

6. Record the data. Find out the average depth of the marble in the solution.

7. Wash and put away all of the materials used.

Conclusion:  We have discovered that the height from which the marble is dropped affects the depth the marble sinks into the polyacrylate. As we said in the hypothesis, they are directly proportional, which means that when the independent variable (height of the starting position) increases, the dependent one (depth of the marble in the solution) also increases. As we can infer from the results (the table) there IS a relationship with the formula of kinetic energy (the higher the starting position is, the more kinetic energy the marble has) and gravitational energy (the higher the marble is, it is pulled with more gravitational force, increasing its energy). Both formulas are proved to be valid.

- References:

Hyperphysics.phy-astr.gsu.edu, (2014). Gravitational Potential Energy. [online] Available at: http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html [Accessed 13 May. 2014].

Physicsclassroom.com, (2014). Kinetic Energy. [online] Available at: http://www.physicsclassroom.com/class/energy/Lesson-1/Kinetic-Energy [Accessed 13 May. 2014].