SCIENCE 101 4.3.4 Lab: Force of Friction Dry Lab Physics Sem 1 Points Possible: 50

Document Content and Description Below

SCIENCE 101 4.3.4 Lab: Force of Friction Dry Lab Physics Sem 1 Points Possible: 50 Force of Friction Materials: · Dynamics track · Spring scale · Friction block · Nylon thread or string ... · Smart pulley (pulley connected to motion detector) · Table clamp · Slotted hanging masses · Force sensor · Computer with graphing software Materials for Exploring Further: · Ballistic cart Procedure Part 1: Determining the Force of Static Friction 1. Connect the force sensor to the computer. Open a graphing software program, and set up the page to record and graph measurements of force versus time. 2. Use the spring scale to determine the mass of the friction block, then record the mass in data table 1. Place the friction block on the dynamics track and connect the block to the force sensor with nylon thread or string. 3. Calculate the normal force (FN) acting on the block and record the value in data table 1. 4. Zero the force sensor to calibrate it. 5. Hold the force sensor so that the string is parallel with the dynamics track. Set the computer to begin collecting data, then slowly pull on the block, steadily increasing the force until the block just barely starts to move. After the block starts to move, continue to pull at a steady rate as the block slides along the track, so that it travels at a constant velocity. 6. Use the graph to determine the force at the breaking point. The peak of the graph is the force at the breaking point, which is the maximum force of static friction. Record this value in data table 1. 7. Repeat steps 2 - 5 three more times, adding mass to the top of the friction block with each new trial. Record the combined mass of the block and mass each time. Be sure to keep the same surface of the block in contact with the dynamics track each time. Data Table 1 Part 2: Determining the Force of Kinetic Friction 1. Make sure you are using the same block-and-track combination as in part 1. 2. Use the computer to set up a graph of velocity versus time. 3. Record the mass of the friction block (mblock) in data table 2, and record the mass of the hanging mass below. Mass of hanging mass (mhanging) = 0.35 kg 4. Calculate the normal force acting on the block: FN = Fw = mblockg. Record this value in data table 2. 5. Set up the track and smart pulley as shown in figure 2 below. Connect the friction block and hanging mass with string. Allow the hanging mass to hang freely off the end of the table. 6. Gently let go of the hanging mass and allow it to pull the friction block across the track. 7. Determine the slope of the graph: . This slope is the acceleration of the falling mass-and-block system. Record the acceleration in data table 2. 8. Use the acceleration (a) of the hanging block to calculate the tension (T) in the string,. 9. Calculate the force of kinetic friction (Ff) on the block: 10. Repeat steps 3 - 6 three more times, adding mass to the top of the friction block with each new trial. Record the combined mass of the block and mass each time. Be sure the keep the same surfaces in contact. Do not add so much mass that the hanging mass is no longer able to pull the block. Data Table 2 Analyze 1. What happens to the normal force as the weight of the friction block increases? Explain your answer. 2. What happens to the acceleration of the hanging mass as the weight of the block increases? Explain your answer. 3. What happens to the tension in the string as the weight of the block increases? Explain your answer. Draw Conclusions 1. What happens to the maximum force of static friction as the weight of the block increases? Explain your answer. 2. What happens to the force of kinetic friction as the weight of the block increases? Explain your answer. Explore Further Part 1 Use a ballistic cart to shoot a small ball into the air. Push the cart along a track, allowing it to release the ball. What explains why the cart always catches the ball, and the ball doesn't fall behind the moving cart? Part 2 How would you expect the results of your experiment to change if you used the same friction block on a different surface? How would you expect your results to change if you set the friction block on a different side (so that the area of contact between the two surfaces was different)? Part 3 Sketch a graph of position versus time for part 2 of the friction block experiment. Approximate the y-intercept and the shape as well as you can. Then sketch a graph of velocity versus time for part 2 of the experiment. Approximate the graph’s y-intercept and its shape as well as you can. Include the slope of the line on the graph. Part 4 1. You and your friends are sledding on a hill. Develop a hypothesis regarding the effects of different factors on your sled speed. 2. Explain how you could perform a controlled experiment to test the hypothesis you proposed in question 1. [Show More]

Last updated: 3 years ago

Preview 1 out of 12 pages