Copy of PHYS110 Resistive Forces Lab - STUDENT VERSION

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Siena College *

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Physics

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Apr 3, 2024

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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 The spring scale pulls the block at a slow constant velocity across the horizontal surface. The spring scale pulls the block at a faster constant velocity across the horizontal surface. What patterns did you notice? Describe as many as you can. 1. When the block started to move, kinetic friction was present 2. When the block was at rest, static friction was present 3. as velocity increased, the force of spring scale on block increased 4. The force of spring scale on block was equal to friction (static or kinetic) 5. normal force is equal to force that earth exerts on the block B. With your group members, discuss the direction and magnitude of the force that the desk exerts on the block in the experiments described above. Does the force have a constant magnitude? Constant direction? How do you know? the force exerted by the desk on the block has a constant magnitude and direction throughout all the events. Its magnitude matches the force exerted by the spring scale and opposite of the motion of the block. 3

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

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