# Stage 2 Physics - Momentum Pracitcal Investigation

Topics: Newton's laws of motion, Momentum, Force Pages: 10 (1299 words) Published: September 3, 2014
﻿STAGE 2 PHYSICS

Assessment Type 1: Investigation Folio
Practical Investigation 2: Momentum

Purpose:
To investigate the relationship between the laws of conservation of momentum and Newton’s Third Law and another variable of your choice for a 2D collision of two objects.

Materials:
Hover puck
Video Recorder
Tripod
Ruler
Tracker (Computer Program)

Method:
On a flat surface containing no
obstacles, prepare the tripod and
camera over the selected area that
the collision will take place
Align masking tape 45 degrees from each corner as a shown above (the arrows). This can be used as a guide for the person releasing the pucks (Optional step) Test the camera angle so that it captures the collision and the before and after speeds. Make sure you have enough room for this Identify and label which puck will be the variable and the one which will be held constant. These pucks must be held constant throughout the entire practical Have a person ready with the camera, while another aligns the pucks in their initial positions. Once ready, signal the camera person, and record the collision at least 3 times Repeat collision altering the variable puck in which ever way you have chosen to do. In our case we added 100g of weight each time. Record each change you make and record them at least 3 times each Analyse the data collected and choose the best video of each variable and begin to import them into the computer program tracker.

Independent and Dependent variable

Independent variable: mass being added to puck b.
Dependent variable: Δp (change in momentum)

Other variables that are held constant in this practical

Mass of puck A - held constant by not altering the weight
Position of camera - held constant by keeping the camera in the same position for each take Release angle of puck - held constant by repeating the same action for each variable

Safety Regulations

This practical contained considerable risk of accidents occurring. In order to maintain a permanent risk free environment, precautions were put in place to ensure ones own safer such as; all equipment was checked twice before recording to confirm stability, all personal was cleared before the pucks were released and the camera mount was used to ensure the camera doesn't fall on a someone or something. Results:

Vector Methods (for 0g Mass)
This is an exact replica of what camera angle was used and the placement of the pucks in our experiment. (angles are obviously not to scale)

Sample Calculation
For 0g Mass

The procedure above was repeated for the following masses and put into the table below.

Results

Graph

Change in momentum against Added Mass

As we can see from the graph the more mass added, the greater the change in momentum occurs. The graph hints that Δp is close to directly proportional to the added mass. Given that this experiment was conducted in an isolated system; which is “a grouping of two or more objects where there is no influence from a net external force that changes the momentum of the system. A net external force may be considered one that is sourced from somewhere other than the objects in the system and is not balanced by (an)other force(s)”, (Physics Classroom, http://www.physicsclassroom.com/class/momentum/Lesson-2/Isolated-Systems) so according to the laws of conservation of momentum (in an isolated system) the initial momentum should equal final momentum. This means there should be no change in momentum (0%). But in the real world, considering gravity there will should always be a loss in momentum, but this is not the case when we consider the propulsion of a rocket. You see if rocket...