Newton’s Laws LabNAMES:
Table #:
Write your answers to these tasks directly into this MS Word file. Please type your answers in
blue text. You MUST include copies of graphs, etc., if it helps. When you are finished, you will submit ONE copy to the group dropbox for the Week 2 Lab.
Setup: Low friction cart on track with motion sensor, force sensor, string, pulley, and weights.
Try to level your track before beginning! A slanted track will skew the results.
Task 1: Rig up the cart so that you can add a weight to the string and it will pull the cart along the track. Determine what hanging mass is needed to get the cart to travel with constant velocity. IMPORTANT NOTE: Like all objects, the cart can tend to “stick” a bit when at rest (friction has this behavior). Thus, when seeking the constant velocity limit, please start the cart with a gentle push to make sure it isn’t just being sticky at rest. You MUST copy appropriate graphs or other data to give evidence for your claim, AND give your reasoning to make the evidence convincing.
Task 2: Keep the same hanging mass as you found in task 1. What do you claim should happen if you give the cart a decent shove toward the pulley so that it is moving substantially faster (but NOT fast enough to damage the equipment!!) than in task 1? Will the cart move at constant speed, will it speed up, or will it slow down as it moves? Explain the reasoning for your claim. Then, practice pushing the cart smoothly so that the mass does not bounce around on the string too much. Once you have mastered this, take a good set of data and only consider the motion that occurs when the push is finished. Present the evidence you gather below. If your prediction was wrong, correct your claim and reasoning.
Task 3: What will happen if you give the cart a push to get it moving away from the pulley? (Again, keep the hanging mass the same as you found in task 1.) Make a claim, collect evidence and explain your reasoning. You must explicitly discuss the forces that would show up in the free body diagram for the cart.
Task 4: What do you claim should happen if you double the pulling mass that you found in task 1? Explain your reasoning. Collect evidence and present it below. If you were wrong, correct your claim and reasoning.
Task 5: What do you claim should happen if you added a 500 g mass to the cart (the carts themselves have a mass of about 510 g) and then repeat the activities of tasks 1 and 4 (you don’t have to repeat 2&3)? What is your reasoning? Collect evidence, present it below, and then modify your claim and reasoning if needed.
Task 6: Now remove the pulley and string and remove the 500 g added mass from the cart. Switch to a fan to drive the motion. Pick high speed for the fan. Practice giving the cart a push so that it turns around and you can get a decent set of data for the turnaround.
Question 6a: Prove to yourself that the acceleration never changes direction during this motion and explain how you can see this in the velocity graph and in the acceleration graph.
Question 6b: How can the cart change direction without the acceleration changing direction?
Question 6c: Take any data you need to and estimate the force of the fan. Show how you did it. NOTE: to quantitatively estimate the acceleration, you must use the slope of the velocity graph. The acceleration graph will be too jittery.
Task 7: Add back the 500 g mass to the cart and then repeat task 6. What happens to the acceleration? Estimate the force of the fan, showing your work. Is it the same force as you found in Task 6?
When you are done: Make sure your names are listed at the top, then email this file to me ().