Copy of PHYS110 Resistive Forces Lab - STUDENT VERSION

Siena College - General Physics 110 Resistive Forces Lab NAME: Emily Brooks GROUP MEMBERS: Lisa, AG, Sylvia, Kahmini Learning Goals 1. In Section I, you will perform observational experiments and analyze them using force diagrams to recognize patterns with respect to the resistive force being exerted on the system. 2. In Section II, you will design experiments to investigate what physical quantities affect the maximum static friction force component of the force that the surface exerts on the object pulled across it. Section I - In this part of the lab, you will perform observational experiments and analyze them using force diagrams to recognize patterns with respect to the resistive force being exerted on the system. Equipment: Graphical Analysis, spring scales or force sensors (Vernier Go Direct Sensor Cart), block of wood with a hook/nail, various masses. Scientific Ability Missing Inadequate Needs Improvement Adequate A5 Force Diagram No representation is constructed. Force diagram is constructed, but contains major errors such as incorrect, mislabeled or not labeled force vectors, incorrect length of vectors, incorrect direction, extra incorrect vectors are added, or vectors are missing. Force diagram contains no errors in vectors, but lacks a key feature such as labels of forces with two subscripts or vectors are not drawn from a single point, or axes are missing. The force diagram contains no errors and each force is labeled so that it is clearly understood what each force represents. B7 Is able to identify a pattern in the data No attempt is made to search for a pattern. The pattern described is irrelevant or inconsistent with the data. The pattern has minor errors or omissions. The pattern represents the relevant trend in the data. A. Work with your group members to perform the experiments described in the table below. Then, analyze them using force diagrams. Describe the patterns that you find. Observational Experiment Force Diagram for the Block Remember that each object interacting with the block exerts one 1

Siena College - General Physics 110 Resistive Forces Lab force on it A block is at rest on the horizontal surface of a desk. A spring scale pulls lightly on the block that is at rest on a horizontal surface; the block does not move. The spring scale pulls harder on the block at rest on the horizontal surface; the block still does not move. The spring scale pulls even harder on the block at rest on the horizontal surface, right before the instant it starts to move. 2

Siena College - General Physics 110 Resistive Forces Lab - we know this because of Newton’s 1st, 2nd and 3rd laws of motion, explain how objects move when forces are acted upon them, our explanations reflect the truths of these - Friction opposes motion and effects how objects stay still or move at a constant speed - when forces balance each other, objects stay still or move at a constant speed - Every action has an equal and opposite reaction C. Resolve the force that the desk exerts on the block into two components: one perpendicular to the interacting surfaces and one parallel. The perpendicular vector component is called the normal force (normal is the term for perpendicular in mathematics) and the parallel vector component is called the friction force. The perpendicular vector of the force that the desk exerts on the block is the normal force to the surface of desk and the block The parallel vector is the force that the desk exerts on the block is the frictional force in contact between the block and the desk. Opposing the motion of the spring scale as it pulls the block. NOTE : You probably noticed that the friction force reached the maximum value right before the block started moving and then decreased a little bit. The friction force that the desk exerts on the block when the block is not moving is called the static friction force. The maximum friction force that the desk can exert on the block right before it starts moving is called the maximum static friction force. The friction force that the desk exerts on the block after the block starts moving is called the kinetic friction force. Section II - In this part of the lab, you will design experiments to investigate what physical quantities affect the maximum static friction force component of the force that the surface exerts on the object pulled across it. Equipment: Graphical Analysis, spring scales or force sensors (Vernier Go Direct Sensor Cart), block of wood with a hook/nail, various masses, various surface materials (sandpaper, printer paper, bubble wrap, wrapping paper, etc.). Work with your group members to design experiments to investigate what 4

Siena College - General Physics 110 Resistive Forces Lab physical quantities affect the maximum static friction force component of the force that the surface exerts on the object pulled across it. With your group, start by discussing which physical quantities you would like to investigate. You are expected to investigate at least 3 separate physical quantities. Purpose & Procedure ● Briefly summarize, in your own words, the objective(s) of your experiments. ● Describe your experimental procedures in enough detail that another group could recreate your experiments exactly -- not just do experiments similar to yours. ● State what you will measure in your experiments as well as the independent and dependent variable(s). Remember not to vary more than one quantity at a time. ● Include a detailed sketch of your experimental setup(s). Scientific Ability Missing Inadequate Needs Improvement Adequate B1 Is able to identify the phenomenon to be investigated No phenomenon is mentioned. The description of the phenomenon to be investigated is confusing, or it is not the phenomena of interest. The description of the phenomenon is vague or incomplete. The phenomenon to be investigated is clearly stated. B2 Is able to design a reliable experiment that investigates the phenomenon The experiment does not investigate the phenomenon. The experiment may not yield any interesting patterns. Some important aspects of the phenomenon will not be observable. The experiment might yield interesting patterns relevant to the investigation of the phenomenon. B3 Is able to decide what parameters are to be measured and identify independent and dependent variables The parameters are irrelevant. Only some of the parameters are relevant. The parameters are relevant. However, independent and dependent variables are not identified. The parameters are relevant and independent and dependent variables are identified. A7 Sketch No representation is constructed. The sketch is drawn, but it is incomplete with no physical quantities labeled, or important information is missing, or it contains wrong information, or coordinate axes are missing. The sketch has no incorrect information, but has either no or very few labels of given quantities. Subscripts are missing or inconsistent. The majority of key items are drawn. The sketch contains all key items with correct labeling of all physical quantities that have consistent subscripts; axes are drawn and labeled correctly. The objective of the experiment is to see the factors that affect the maximum static friction force between an object and various surfaces. We want to understand how different surfaces influence the max static friction. We then 5

Siena College - General Physics 110 Resistive Forces Lab Mass of object/change normal force constant surface object mass max static friction wooden block 0.237kg 0.5N wooden block + 1 block 0.742kg 2.0N wooden block + 2 block 1.255kg 3.5N wooden block + 3 block 1.764kg 5.5N wooden block + 4 block 2.276kg 6.5N wooden block + 5 block 2.780kg 9.5N Calculations of the normal force: N force = - F_E on B = - mg = - m * (-9.8 N/kg) = m * 9.8 N/kg 1) 0.237 kg * 9.8 N/kg = 2.3226 N 2) 0.742 kg * 9.8 N/kg = 7.2716 N 3) 1.255 kg * 9.8 N/kg = 12.299 N 4) 1.764 kg * 9.8 N/kg = 17.2872 N 5) 2.276 kg * 9.8 N/kg = 22.3048 N 6) 2.788 kg * 9.8 N/kg = 27.3224 N Graph(s) ● Include as many graphical representations as needed to further analyze your data . At least one of the physical quantities you investigated will benefit from the creation of a graph. The other physical quantities may not require you to make a graph - please consult with your instructor. ● Remember to include a trendline to fit your data as this is an important step towards being able to analyze your data and finding a relationship between the quantities being graphed. ● What is the physical meaning of the slope of your graph? 7

Siena College - General Physics 110 Resistive Forces Lab Figure 1: The slope on the graph shows that as the normal force increases, the static friction increases as well. On the x axis is the normal force of the object, which the y axis (static friction) is dependent upon. Scientific Ability Missing Inadequate Needs Improvement Adequate A11 Graph No graph is present. A graph is present, but the axes are not labeled. There is no scale on the axes. The data points are incorrectly connected to each other instead of using an appropriate trendline. The graph is present and the axes are labeled, but the axes do not correspond to the independent and dependent variable OR the scale is not accurate. The data points are not connected to each other, but there is no trendline either. The graph has correctly labeled axes, the independent variable is along the horizontal axis and the scale is accurate. The trendline is correct. Data Analysis 8

Siena College - General Physics 110 Resistive Forces Lab environmental factors (air resistance, temperature etc) These factors could lead to inconsistencies in measurements and affect the reliability of our graphed and collected results. 10