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Transcript

Name: _______________________________________ Block: ____________ Date: _____________ Conceptual Physics-Newton’s 2nd Law Lab Mr. White Newton’s 2nd Law Lab OBJECTIVE Students will investigate the relationship between Net force, Acceleration and Mass. Background Newton's second law relates the acceleration of an object to the force that produces it. This experiment uses the gravitational force on a falling mass to propel a box with masses inside across the table. During the experiment you will provide evidence that supports the equation for Newton’s second law. A net force must be applied to a mass to produce acceleration. Acceleration is a change in velocity, a positive acceleration increases velocity (speeds up a mass), a negative acceleration decreases velocity (slows down a mass). Acceleration is the rate of change of velocity per second; it has units of meters/second per second or meters/second 2. Newton's Second Law relates force, mass and acceleration. a = F/m or F = ma where: F is force in Newtons m is mass in kilograms a is acceleration in meters/sec2 Materials Per Lab Group 1 Dynamics Cart 1 Wireless Dynamics System (WDSS) Different Masses Digital Balance Calculator Pulley Dynamics Cart Track Name: _______________________________________ Block: ____________ Date: _____________ Conceptual Physics-Newton’s 2nd Law Lab Mr. White Pre-Lab Questions 1. What is the equation that represents Newton’s Second Law of Motion? ____________________ 2. A student pulls on a wagon that has a constant mass, if the student pulls twice as hard on the wagon, how will that affect the acceleration of the wagon? ______________________________________________________________________________ 3. A small child is pushing a shopping cart that is empty. Their mother fills the cart with bottles of water, increasing the mass of the cart three times its empty mass. How will this affect how fast the child can accelerate the cart? ______________________________________________________________________________ 4. Using any resource at your disposal, sketch a line graph that represents a DIRECT relationship and an Inverse Relationship between variable. Direct Relationship 5. Inverse Relationship Using your notes from UNIT 1, how can I use a Velocity – Time Graph to find the acceleration of an object? __________________________________________________________________________________ 6. Draw a free body diagram of the forces acting on the cart and the hanging weight in the diagram below. Assume that the cart is frictionless. FBD for Mass 1 FBD for Mass 2 7. What force is responsible for making the cart accelerate in question 5? __________________________________________________________________________________ Name: _______________________________________ Block: ____________ Date: _____________ Mr. White Conceptual Physics-Newton’s 2nd Law Lab Procedure Sheet PART 1: In this experiment you will investigate the relationship between MASS and ACCELERATION for a constant FORCE. 1. Setup the Equipment. a. Turn on the LabQuest. b. Place the track on a level surface and connect the Motion Detector to the USB port of the Labquest 2. c. On the LabQuest, select the small Graph Icon at the top of the screen to change to the graph window. d. Show only the Velocity Graph. i. Graph Show Graph Graph 2 e. Place the dynamics cart on the center of the track. If the cart begins to roll, adjust the feet on the track to level it. 2. Take the cart to the digital balance and measure the mass of the cart. Record this value in the observation table. This value must be record in KILOGRAMS. 3. Hang the 20 g. mass on the string. The weight of this mass will create a force to move the cart. Using the equation for weight, calculate this force and record it in the observation table. You must convert the 20 g mass to kilograms before putting it into the equation. 4. Pull the cart back so that when you release it and hold it in place. 5. Press Play on the Labquest. When you hear the “clicks” from the detector, release the cart. The Labquest should begin showing the position and velocity data of the cart. 6. Collect the average acceleration of the cart by completing the following steps. a. Highlight the region of the VELOCITY graph that is linear and shows a constant positive acceleration. (See Figure 1). b. Select the Analyze Menu Curved Fit Velocity c. When the new window shows up, select “Linear” under the “Choose Fit” tab. d. Record the slope (m), this represents the average acceleration of FIGURE 1 the cart. 7. Now place a 200 g mass on the cart. Record the new value of the mass in the observation table. 8. Repeat the data collection for the acceleration. 9. Repeat the experiment adding 200 g to the cart each time until you have collected data for 4 total trials. Name: _______________________________________ Block: ____________ Date: _____________ Mr. White Conceptual Physics-Newton’s 2nd Law Lab PART 2: In this experiment you will investigate the relationship between FORCE and ACCELERATION for a constant MASS. 1. Record the mass of the cart in the observation table. 2. Hang the 10 g mass on the string. Calculate the weight on the string in Newtons and record this in the observation table. Remember the mass must be in KILOGRAMS to use the weight equation. 3. Collect the acceleration of the cart the same way as you did in Part 1. 4. Repeat the experiment with the 20 g, 50 g and 100 g mass hanging on the string. Name: _______________________________________ Block: ____________ Date: _____________ Conceptual Physics-Newton’s 2nd Law Lab Mr. White Observation and Data Collection Sheet PART 1: OBSERVATION TABLE Trial Hanging Weight (N) Mass of Cart (kg) Average Acceleration 1 2 3 4 PART 2: OBSERAVTION TABLE Trial Mass of Cart (kg) Hanging Mass (g) 1 10 2 20 3 50 4 100 Hanging Weight (N) Acceleration (m/s2) Name: _______________________________________ Block: ____________ Date: _____________ Conceptual Physics-Newton’s 2nd Law Lab Mr. White Data Analysis & Understanding Sheet PART 1: Create a Line Graph that shows how acceleration is affected by the mass of the cart. Make sure you graph included the following. a. Title b. Labels axis with the units of measurement. c. An appropriate scale on the two axis. Part 2: Create a Line graph to display how the force acting on the cart affect the carts acceleration. Name: _______________________________________ Block: ____________ Date: _____________ Mr. White Conceptual Physics-Newton’s 2nd Law Lab Identify the Independent, Dependent and at least two Constants for the experiments done in this lab. Part One: Part Two: I.V. _________________________________________ I.V. _________________________________________ D. V. _______________________________________ D. V. _______________________________________ Two Constants: Two Constants: _________________________________ _________________________________ ________________________________ ________________________________ Looking at the graph from the analysis of Experiment ONE, what happens to the acceleration of an object if the mass of the object increases? _____________________________________________________________________________________ Looking at the graph from the analysis of Experiment TWO, what happens to the acceleration of an object if the force acting on the increases? _____________________________________________________________________________________ Use your graph from Part 1 to answer the following question. Although we never tested having 500 g of mass on the cart, theoretically what would have the acceleration of the cart have been? _____________________________________________________________________________________ Use your graph from Part 2 to answer the following question. How much would the hanging weight need to way to make the cart accelerate at 1.0 m/s2? _____________________________________________________________________________________ Based off the relationships observed in this lab, if a small car (small mass) and a large truck (large mass) were stopped at a red light, which vehicle’s engine must provides more force to make the vehicle accelerate? ____________________________________________________________________________________ Based off the relationships observed in this lab, two identical trucks were stopped at a red light (so the same force of an engine), but truck one is pulling a trailer, which truck will accelerate faster when the light turns green? The truck with the trailer or the one without the trailer? _____________________________________________________________________________________