Lab Assignment 3: Newton’s Laws
Newton’s laws of motion are a central component of our understanding of physics. As we discussed in Module 5, Newton’s laws can be summarized as follows:
In this lab, you will perform experiments to explore each of the laws of motion.
This activity is based on Lab 5 of the eScience Lab kit. Although you should read all of the content in Lab 5, we will be performing a targeted subset of the eScience experiments.
Our lab consists of three main components. These components are described in detail in the eScience manual (pages 55-61). Here is a quick overview:
Note: Record all of your data in the tables that are provided in this document.
Take detailed notes as you perform the experiment and fill out the sections below. This document serves as your lab report. Please include detailed descriptions of your experimental methods and observations.
Newton’s First Law – Water in a Bowl
· I recommend that you perform this experiment outdoors as there most likely will be some spillage of water.
Newton’s Second Law – The Atwood Machine
· Prior to determining the mass of the washers, make sure to zero your spring scale. To zero your spring scale, hold it vertically with no mass attach and turn the top screw until the scale reads 0 grams. Refer to the following picture:
[img width=”189″ height=”255″ src=”file:///C:/Users/srarin/AppData/Local/Temp/msohtmlclip1/01/clip_image004.jpg” alt=”Description: SpringScale” v_shapes=”Picture 4″>
· You may want to use the hooks on the pulley to hang your Atwood machine. I placed mine on a hanger:
[img width=”301″ height=”226″ src=”file:///C:/Users/srarin/AppData/Local/Temp/msohtmlclip1/01/clip_image006.jpg” alt=”Description: Atwood” v_shapes=”Picture 3″>
Newton’s Third Law – Balloon-Powered Vehicle
· Here is a picture of my balloon-powered vehicle:
[img width=”287″ height=”211″ src=”file:///C:/Users/srarin/AppData/Local/Temp/msohtmlclip1/01/clip_image008.jpg” alt=”Description: Balloon” v_shapes=”Picture 2″>
· To add mass, I taped washers to the straw.
Material and Methods
Data table for the Atwood Machine experiment (Experiment 2, Procedure 1):
Height = __ meters
Mass of 15 washers = __ grams
Mass of 1 washer = __ grams
M1 = __ grams (lighter mass)
M2 = __ grams (heavier mass)
Fall time (sec)
Calculated acceleration (m/s2)
Analysis and Discussion
Note: Make sure to show your calculation for the acceleration.
Based on your experimental results, please answer the following questions:
Explain how your observations of the water demonstrate Newton’s law of inertia.
Draw a free body diagram of your containers of water from the situation in Step 3d (After walking in a straight line at constant speed, stop abruptly). In your free body diagram, draw arrows for the force of gravity, the normal force (your hand pushing up on the container), and the stopping force (your hand decelerating the container as you stop.) What is the direction of the water’s acceleration?
Describe two instances where you feel inertial forces in a car.
Draw a FBD for M1 and M2 in your Atwood machine. Draw force arrows for the force due to gravity acting on both masses and the force of tension
[img width=”267″ height=”356″ src=”file:///C:/Users/srarin/AppData/Local/Temp/msohtmlclip1/01/clip_image009.jpg” alt=”Description: Atwood_Machine” v_shapes=”Picture 1″>
Use Newton’s Second Law to write an equation for each mass of the Atwood machine. Solve these two equations for the acceleration of the system.
Using the masses M1 and M2, use the above expression to calculate the acceleration of the system. How does this value compare to your experimentally measured acceleration? What factors may cause discrepancies between the two values?
Explain what caused the balloon to move in terms of Newton’s Third Law.
What is the force pair in this experiment? Draw a free body diagram to represent the (unbalanced) forces on the balloon/straw combination.
Add some mass to the system by taping some metal washers to the guide straw and repeat the experiment. How does this change the motion of the assembly? How does this change the free body diagram?
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