Newton s Second Law. Equipment List: PASCO track, Photogate dynamics cart, pulley and clamp, masses, Pickett fence, string, bumper, paper clips.

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1 Newton s Second Law Purpose: The purpose of this Lab Activity is to guide you with the experimental verification of Newton s second law represented by the equation F = ma, where F is the net force action on an object, m is the mass of the object, and a is the acceleration of the object as a result of F. This Lab Activity is intended to assist you to: Develop a physical understanding of the relationship between force and acceleration. Make experimental measurements and use graphical analysis to confirm Newton s second law. Equipment List: PASCO track, Photogate dynamics cart, pulley and clamp, masses, Pickett fence, string, bumper, paper clips. Bring Ruler, pencil, calculator, textbook

2 Newton s Second Law Name (observer): Date: / / Name (partner): Course # and Section Name (partner): Activity 1 A cart is made to roll on a horizontal level track. Draw a labeled free body diagram of the cart only and from it write down an expression from Newton s II law. Explain what each term in the expression is. Activity 2 Using the equipment provided, one can design and conduct an experiment to calculate the acceleration of the cart for any applied force. Show that one can use kinematics to do this without using the computer. Clearly state your initial conditions.

3 Activity 3 A cart is made to roll on a horizontal level track with the help of a falling mass as shown in the diagram. Draw properly labeled free body diagram(s) and derive an expression for the acceleration of the cart. Assume that the paper clips represent the falling mass for this activity. This expression for acceleration (a T ) gives you the theoretical value. (Hint: your textbook will be useful here)

4 Activity 4 Design and conduct an experiment to find acceleration of the cart for various applied forces. Use the equipment that is available to you including the sensors and the data studio software. Find out how many paper clips does it take to get the cart just rolling (think why you need to do this). Then use additional weights to apply various forces and find the acceleration. This will be your experimental value (a E ). Note that the sensors will give you more accurate results (if used properly) than the process of activity 2. Organize your work in data tables provided here. Caution: The total of mass on the hanger + on the cart should not exceed 80 grams at any time. DATA TABLES Note: You are expected to know and learn how to make appropriate tables to represent scientific data. However I will provide them to you this time to assist you and as examples for future experiments. Table 1: Various Masses A B C 1 Item Mass (g) Mass (kg) 3 Mass of the cart (m C ) 4 Mass of all weights Mass of Pickett Fence (m p ) Mass of the Hanger (paper clips) (m h ) 6 Total of all masses m total Table 2: Experimental Acceleration Distance between Photogates : (cm) (m) 1 *Mass (m) on hanger (kg) A B C D E F Mass on a E -Trial 1 a E -Trial 2 a E -Trial 3 Cart m/s 2 m/s 2 m/s 2 (kg) * This includes the mass of the hanger Note: Mass of hanger + Mass on hanger + Mass on Cart should be within 80g-85g. Did you notice I have odd number of data run and trials for each run why? Average a E m/s 2 Table 3: Net Force A B C D E 1 *Mass (m) on hanger (kg) a T (m/s 2 ) a E (m/s 2 ) % Error F net (N) * This includes the mass of the hanger Average % Error:

5 Activity 5 Determine the percentage error (column D of table 3) between your theoretical value and the experimental value of acceleration. State under what condition (or assumption) this calculation is valid. Do you have a high or a low percentage error? Explain your results. Activity 6 Regardless of the percentage error in activity 5, one can use the experimental data and the analysis in activity 1 to avoid putting conditions (or making assumptions) for calculation in activity 5. Use your experimental data to plot a graph of net force verses (F net ) experimental accelerations (a E ). From your graphs deduce the coefficient of static friction and redo the calculation in activity 5. What is now the new average percentage error? Show all relevant work here. Include a print out of your graph with any relevant regression performed. You can do regression in either Data studio or in Excel.

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