Pencil Penetration and WaterBackground:Laws and Principles involved:Newtons third law: When one body exerts a force on a second body, the second simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body. In laymans terms, for every action there is an equal and opposite reaction.Buoyancy: An object that is less dense than the fluid it is in will float to the top.

Types of Energy that occur:Kinetic Energy:The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.It can be calculated using the formula:

Potential Energy:The energy that is stored in an object due to its position. It is the energy difference between the energy of an object in a given position and its energy at a reference position.

Various factors that may affect the penetration of the pencil in water such as: Surface tension of the water Which side the pencil is dropped Whether the pencil is sharpened Air resistance Density of object and fluid Buoyancy

Investigation Section:Investigative Plan:I will be researching the factors that may affect the penetration of the pencil in water, the forces it experiences, the different types of energy that occur, risk and a way of approaching this experiment. Factors that may affect the penetration of the pencil in water, and the different types of energy that occur are shown above. The controlled variables in this experiment are the amount of water, and the use of the same equipment to decrease the amount of incidental errors that may occur when performing this experiment.

The forces an object experiences when falling in water:When an object falls in water, it will experience an opposite resistance force that will eventually stop the object. Objects falling from different heights will have different speed and energy, and thus can have different depth of penetration in water. When the object is dropped higher than previously, there will be an increase in the amount of potential energy, thus having and increased amount of kinetic energy on impact.

Ensuring accuracy and reliability:Reliability: Repeating the experiment, and using the average of the results.Accuracy: Using a clamp and retort stand to drop the pencil to ensure that the pencil is not shaking and is parallel to the measuring cylinder, reducing inaccurate results that may occur. Also, using the mL marks on the measuring cylinder may aid in improving the accuracy of the results.

Statement of Variables:Independent Variable: height pencil is droppedDependent Variable: depth pencil penetrates waterControlled Variable(s): amount of water, same apparatus used

Experimental Approach:The experiment will consist of dropping a pencil using a stand and clamp into a measuring cylinder. When recording my results, I will use a ruler, but if the pencil penetrates the water further than 30cm, I will use the mL increments to calculate my results.HazardRiskHow it will be minimised

Glass Measuring CylinderMinor lacerationsHandle glass measuring cylinder with care

PencilVery minor puncturesDo not point or stab with pencil

Aim:To determine how the depth to which a pencil penetrates water varies with the height from which it dropped.

Hypothesis:The greater the height the pencil is dropped, the greater the depth to which the pencil penetrates water.

Equipment: Pencil: the object to conduct the experiment 1L measuring cylinder: used to decrease the possibility of the pencil dropping down to the bottom of the water by getting a taller measuring cylinder to drop it in. It also is used for the mL markings to help measure the depth the pencil penetrates water if it drops beyond 30cm, ensuring more accurate results. Ruler: used to measure the depth the pencil penetrates water Stand and Clamp: to keep the pencil parallel with the measuring cylinder, reducing any inaccurate results that may occur.

Method:1. Prepare the equipment as shown in the diagram below.2. Fill the measuring cylinder up _______mL.3. Drop the pencil in the water and pick it back up.4. Place the pencil 1cm above the water using the clamp5. Drop the pencil.6. Observe and record your results.7. Reset the position of the pencil8. Drop the pencil.9. Observe and record your results.10. Increase the height of the pencil by ____cm.11. Repeat steps 5-9 twice.12. Increase the height of the pencil by ____cm.13. Repeat steps 5-9 twice.14. Increase the height of the pencil by ____cm.15. Repeat steps 5-9 twice.16. Increase the height of the pencil by ____cm.17. Repeat steps 5-9 twice.

Diagram:

Pencil

Stand and Clamp

Measuring Cylinder

Water

Results:Distance between mL increments: ________________________cmHeight of pencil above water (cm)Depth the pencil penetrates the water (cm) (distance between mL increments x mL penetration) (cm-1)

Trial 1Trial 2Average

Bibliography:Physics Workbook.Newton's Third Law. 2013.Newton's Third Law. [ONLINE] Available at: http://www.physicsclassroom.com/Class/newtlaws/u2l4a.cfm. [Accessed 10 August 2013].Potential Energy. 2013.Potential Energy. [ONLINE] Available at:http://www.physicsclassroom.com/Class/energy/u5l1b.cfm. [Accessed 11 August 2013].Kinetic Energy. 2013.Kinetic Energy. [ONLINE] Available at:http://www.physicsclassroom.com/Class/energy/u5l1c.cfm. [Accessed 11 August 2013].