8A_Lab2_ForcesAndAccelerations

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LAB 2 Forces And Accelerations In this laboratory, we will be analyzing a spring scale and a cart and track system with a various assortment of masses. The goal of this lab is to better familiarize you with Newton’s Laws as well as forces and accelerations in general. Given Quantities • Track Length = 0.8m • Mass of Weight Hook = 5g • Mass of Cart = 520g • Mass of Pulley = 30g • Mass of String º 0.5g • Mass of Rectangular Metal Block = 500g 2.1 Analyzing Net Force And Accelerations In this part of the lab, we will try to better understand the relationship between forces and accelerations by using a mass and a spring scale. As background, a spring scale works in a similar fashion to an ordinary household scale. When a weight is attached to it, its spring stretches and the scale displays the weight of the attached object in units of Newtons. Figure 2.1: 500 Gram Mass on Spring 105

2. F ORCES A ND A CCELERATIONS 1. Take the 500g mass (or another mass that you have been provided) and attach it to the end of the spring scale. Because the spring scales may not be totally accurate, record the reading on the scale in the space below. 2. Draw a Free Body Diagram for the mass and spring scale system while it is at rest in the space below. Include the “Force of the Scale” and “Weight of the Mass”. Indicate the relationship between these two forces. Figure 2.2: Moving Scale 3. Before we proceed any farther, let’s do a quick thought experiment. What would happen to the reading of the scale if you were to move the scale up or down with a constant velocity, while the mass was attached (but without touching the mass)? Would the reading on the scale increase, decrease, or stay the same? Briefly explain your reasoning. 4. Now, with the 500g mass attached, hold the scale and move it up and then down with a constant velocity. What happens to the reading of the scale as you do so? Was your group’s hypothesis correct? If not, explain why. 5. Draw a Free Body Diagram for the mass and scale system as it is moved with constant velocity. Indicate the relationship between the “Force of the Scale” and “Weight of the Mass” and indicate the direction of acceleration if applicable. 6. Before we proceed any farther, let’s do another quick thought experiment. What would happen to the reading of the scale if you were to move the scale up from the floor to approximately shoulder level rather quickly? Would the reading on the scale increase, decrease, or stay the same? Briefly explain your reasoning. 7. With the 500g mass attached, one teammate will hold the scale (with mass still attached) close to the ground and then move it up to shoulder level rather quickly. The rest of the team will observe the reading of the scale. What happens to the reading of the scale as the mass is moved quickly upward? Was your group’s hypothesis correct? If not, explain why. 106 470g The force of the spring scale and the weight Force of scale of the massare the same magnitude Gravity's force pulls down on the mass while the spring pushes up on it weight of masi Moving the entire system upward would cause the weight tobe heavier since the object is moving against gravity The scale read a heavier weight as we moved the system up showing that our hypothesis was correct 1 Egg L thereis zero acceleration when velocity is constant The reading on the scale would increase since thenet force will no longer be zero due to the increase of upward force on the spring with upwardacceleration

2.1. Analyzing Net Force And Accelerations 8. Draw a Free Body Diagram for the mass and scale system as it is moved upward quickly from the floor. Indicate the relationship between the “Force of the Scale” and “Weight of the Mass” and indicate the direction of acceleration if applicable. 9. Before we proceed any farther, let’s do another thought experiment. What would happen to the reading of the scale if you were to move it from shoulder level to the floor rather quickly? Would the reading on the scale increase, decrease, or stay the same? Briefly explain your reasoning. 10. With the 500g mass attached, have one teammate hold the scale and mass at shoulder level then have them move it toward the ground rather quickly while the rest of the team observes the reading of the scale. What happens to the reading of the scale as the mass is moved quickly downward? Was your group’s hypothesis correct? If not, explain why. 11. Draw a Free Body Diagram for the mass and scale system as it is moved downward quickly. Indicate the rela- tionship between the “Force of the Scale” and “Weight of the Mass” and indicate the direction of acceleration if applicable. 12. Using the principles you learned above explain how someone would feel in an elevator as it initially moves upward, as it is traveling upward, and as it comes to a stop. Specifically, explain whether someone would feel lighter, heavier, or the same weight at these three points and briefly explain why using a combination of Free Body Diagrams and brief explanations. 107 My hypothesis was correct since the reading on the scale increases quite rapidly and by a large margin as the scale is quickly moved upwards acceleration is present in the upwards I force of scale direction force of mass The reading on the scale will decrease because the net force will no longer be zero because the downward forcewhich used tobe just the weight ofthe mass mxg would now include the downward acceleration My hypothesis was correct because the reading on the scale decreases rapidly When we move the scale downwards acceleration is force of scale present in the downwards direction weight of mass initially movesupward travellingupward coming to a stop force of elevator f In elevator of long of elevator mass force is greater in downwards direction The movement would be at a constant making net force negative which makes velocitymeaning zero acceleration in Acceleration is in the upwards dirite either direction andthat both present causing you to feel heavier than you feel lighter thannormal forces are equal You will feel the same normal

2. F ORCES A ND A CCELERATIONS 2.2 Newton’s First Law / Analyzing Simple Accelerations Take your track and place it flat against the table, and then place your cart on the track. Ensure that the track is flat and level, and that the cart can remain at rest while on the track. Adjust the track as necessary. Ensure that the “Bubble Level” is securely attached to the cart using the piece of putty, and that the bubble is centered between the lines when the cart is at rest i.e. that the level is parallel to the table. Assume that all surfaces are perfectly smooth, which means the cart does not slow down due to friction. Refer to the picture below. Figure 2.3: Cart on Level Track 1. Briefly explain Newton’s First Law and provide an every-day example below. 2. Before we begin the next part of the lab, let us briefly think about what is inside of a bubble level. Consider that a bubble level contains some sort of fluid, and some sort of gas. For our purposes, we can assume that the level contains a combination of water and air. Which of these components likely has more mass, the water or the air bubble? Now we are going to try and make some predictions. For each of the motions described below, predict where the bubble will be in the level and sketch the location of the bubble within each box. For each case, try and briefly explain your prediction. It may also be helpful to think about what happens to the fluid that is in the level during these time periods. Case 1: Cart moves to the right and is speeding up. Case 2: Cart moves to the right with constant velocity. Case 3: Cart moves to the right and is slowing down. Explanation: Explanation: Explanation: Now you will try it out. Take your cart and place it at the end of the track farthest away from the bumper. With your hand, give the cart a gentle but quick tap toward the end of the track with the bumper. 1. While your hand is pushing the cart, sketch the position of the bubble. What can you say about the cart’s 108 an object stays in motion or at rest unless acted upon by an outside force 16 skating An object stays at motionor at rest unless acted upon by an outside force ie Ice skating Water has a higher mass than the air bubble iii EEd.name immuna shift shifting it mass shift

2.2. Newton’s First Law / Analyzing Simple Accelerations acceleration during this time, is it zero or nonzero? Draw a Free Body Diagram of the cart at this time and if applicable, draw an arrow that points in the direction of the cart’s acceleration. 2. After your hand is no longer touching the cart and it is moving toward the bumper, sketch the position of the bubble. What can you say about the cart’s acceleration during this time, is it zero or nonzero? Draw a Free Body Diagram of the cart at this time and if applicable, draw an arrow that points in the direction of the cart’s acceleration. 3. What happens to the position of the bubble the moment the cart hits the bumper? Sketch the position of the bubble. What can you say about the cart’s acceleration during this time, is it zero or nonzero? Draw a Free Body Diagram of the cart at this time and if applicable, draw an arrow that points in the direction of the cart’s acceleration. 4. Using Newton’s first law, try to explain what is happening to both the bubble and the fluid during the different periods of motion. Were your predictions correct? 2.2.1 Newton’S First Law / Analyzing Accelerations Due to Gravity Take your track and place it on the metal bar so that it is inclined at a small angle of about 15 degrees. Make sure that the black bumpers underneath the track are behind the metal bar, to ensure that the track will not slide off during the next part of the laboratory. While the cart is resting on the inclined track against the bumper, adjust your Bubble level so that the bubble is positioned in the center between the two lines while the cart is at rest. Meaning, the level should be parallel to the table, even though the cart is now on an incline. Assume that all surfaces are perfectly smooth, which means the cart does not slow down due to friction. Figure 2.4: Cart on a Sloped Track Like before, we are going to try and make some predictions. For each of the motions described below, predict where the bubble will be in the level and sketch the location of the bubble within each box. For each case, try and briefly explain your prediction. It may also be helpful to think about what happens to the fluid that is in the level during these time periods. 109 The acceleration is nonzero positive Fhand dairy oh I 1mg The acceleration iszero offing The acceleration is nonzero negative Fumff Ing s direction of deacceleration My predictions werecorrect

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