Little Scientists: abril 2014

21/04/2014

Lab experiment (by: María Gallego)

Research question:

How does height affect to the impact of an object over sodium polyacrelate?

Hypothesis:

My hypothesis is that the higher the altitude the object is dropped from, the higher the velocity it will reach, resulting in a greater impact force and a larger crater in the sodium polyacrelate compound.

Any free falling object has an acceleration of - 9.8 m/s².Therefore, as the height increases more and more, the object will have more distance to accelerate and it will reach a higher velocity.

A vector is a geometric quantity which has a magnitude and a direction. A momentum is the product of the mass and velocity of an object. It is a vector, as it has a direction and a magnitude. (Physicsclassroom.com, 2014)

The physicist Isaac Newton developed a theory to get rough approximations of the impact depth of projectiles travelling at high velocities. I know a 5g ball of marble is not the same as a projectile, but the idea is the same.

When we let the ball fall to the ground, it has an acceleration of 9.8m/s2 due to gravity. Each second, the velocity of the ball increases. When it reaches the floor it has a momentum which is equal to its mass (2kg) times its final velocity. In order to stop the ball, this momentum must be transferred into another mass, this is the mass directly in front of the ball (sodium polyacrelate), which will be pushed depending of the ball’s velocity. The higher the velocity the further the plasticine will be pushed. The impact depth depends on the mass and the velocity of the impactor. The impactor (the ball) will stop when its momentum is transferred to the sodium polyacrelate compound, this is, when it penetrates in the sodium polyacrelate, a depth that is equal to its own length times its relative density divided by the density of the mixture. (Physics.le.ac.uk, 2014)

D= depth; A= density of the impactor (ball); B= density of the target mass (sodium polyacrelate); L= length

D= L·(A/B)

The velocity (v) of a falling body that falls from rest is found by multiplying g by the time (t) during which a body falls: v = gt

The impactor, the ball, is a vector, as it has a magnitude (its length) and a direction

With this I conclude that the height (factor) is directly proportional to the impact depth (effect), as the higher we throw the ball from, the higher velocity it will get, resulting in a higher momentum which leads to a greater impact causing a larger crater.

Variables

Independent variable: height (o.5m, 1m, 1.5m , 2m, 2.5m)

Dependent variable: depth of the crater in sodium polyacrelate

Controlled variables: mass (5g), force (the only force that will be applied at the ball will be gravity), direction (it will have a straight fall), shape (round), material of the ball (marble), material where the ball will fall (sodium polyacrelate).

Materials

Sodium Polyacrelate

5g plastic ball

Bench

Beaker

Ruler

A friend

Method:

1. Put a 250mL beaker filled with sodium polyacrelate just where you are going to drop the ball.

2. Climb a ladder so you are 0.5 meters above the brick of plasticine. Measure the distance with a ruler between the brick of plasticine and the point where you are going to drop the ball from.

3. Have a friend next to the beaker so that he/ she chronometers the time the ball takes to reach the floor.

4. Drop the ball (without adding any force).

6. Get down of the ladder and measure the crater the ball has made in the compound.

7. Measure with a ruler the crater the ball has made.

8. Write down the results in the notebook.

9. Repeat the same process but increasing the height (o,5m, 1m, 1.5, 2m, 2.5m)

Data:

Graph: Height (from where I drop the ball)- Depth of the crater

Table: Height (from where I drop the ball)- Depth of the crater

Height (m)	0.5					1
Height of the crater (cm)	1	2	3	4	5	1	2	3	4	5
Height of the crater (cm)	1.2	1	1.2	1.4	1.4	2	2.5	2.5	2.5	2.3
Average (cm)	1.24					2.36

1.5					2					2.5
1	2	3	4	5	1	2	3	4	5	1	2	3	4	5
4.5	4.7	5	5	4.9	3.5	4.0	4.1	4.0	4.5	5.0	5.0	5.1	5.3	5.5
4.82					4. 02					5.18

Conclusion and evaluation:

The results of this experiment, which are shown at the table and the graph, support the hypothesis that the higher the altitude the object is dropped from, the larger the crater in the sodium polyacrelate compound will be. With the graph we can easily see that between the height from where the ball is dropped and the depth of the crater there is a proportional relationship, if the height increases the depth does too, and vice versa.

However, the alignment of the dots at the graph is not perfect. This could be due to mechanical error during the procedure. The accuracy of the results could be improved using a larger recipient, as the one we used was so small that it was very difficult to hit in the sodium polyacrelate solution with the marble. The error may have also occurred due to the lack of accuracy we had during the measurements as much to the height the ball had to be dropped from as to the depth of the crater.

Finally, with this experiment I was able to answer my research question, not only by looking up the information in the internet (from where I got my information for backing up my hypothesis), but also by verifying it myself and confirming it with an experiment.

Bibliography:

Bbc.co.uk. 2014. BBC - GCSE Bitesize: Gravitational potential energy (GPE). [online] Available at: http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/forces/themeridesrev1.shtml [Accessed: 17 Feb 2014].

Diangco, M. and Profile, V. 2014. Free Fall Motion: Kinematic Equations for Free Fall. [online] Available at: http://motionfreefall.blogspot.com.es/p/kinematic-equations-for-free-fall.html [Accessed: 19 Jan 2014].

Education.com. 2014. Does Height or Distance Affect Impact? | Education.com. [online] Available at: http://www.education.com/science-fair/article/does-height-or-distance-affect-impact/ [Accessed: 21 Jan 2014].

Hyperphysics.phy-astr.gsu.edu. 2014. Energy of falling object. [online] Available at: http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html [Accessed: 19 Jan 2014].

HowStuffWorks. 2014. HowStuffWorks "Falling Bodies". [online] Available at: http://science.howstuffworks.com/falling-bodies-info.htm [Accessed: 17 Feb 2014].

Physicsclassroom.com. 2014. Kinematic Equations and Free Fall. [online] Available at: http://www.physicsclassroom.com/class/1dkin/u1l6c.cfm [Accessed: 21 Jan 2014].

Physicsclassroom.com. 2014. Vectors and Direction. [online] Available at: http://www.physicsclassroom.com/class/vectors/u3l1a.cfm [Accessed: 17 Feb 2014].

Physics.le.ac.uk. 2014. [online] Available at: https://physics.le.ac.uk/journals/index.php/pst/article/viewFile/589/403 [Accessed: 17 Feb 2014].

S-cool.co.uk. 2014. GCSE Physics Energy Calculations Revision - Gravitational Potential Energy | S-cool, the revision website. [online] Available at: http://www.scool.co.uk/gcse/physics/energy-calculations/revise-it/gravitational-potential-energy [Accessed: 17 Feb 2014].

Logger pro 3

This is a graph made with logger pro 3. The data is obtained from this video:

lunes, 21 de abril de 2014