PHYS 223 - Lab Report 5 (Projectile Motion)

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University of Louisville *

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223

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Mechanical Engineering

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Feb 20, 2024

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PHYS 223 Projectile Motion Megan Cousins Tuesday-Thursday Objective Our goal for this lab was to explore the force of friction as a difference in the force required to pull a cart up an incline and release the cart down the incline with little to no acceleration. Introduction For this experiment we worked with the work energy theorem that states that the work done by non- conservative forces is equal to the change in the total mechanical energy of the system. In two different parts, we measured frictional forces by using the fact that at a constant velocity the acceleration of the systems is zero. And during the second part, finding the frictional force by measuring the work done which is equal to the change in the total mechanical energy of the system. Questions 1. Calculate the velocity, change in energy and f for all parts and cases. v = 0.278, ΔE = -0.4597, f = 0.4788 2. Identify exactly where the f comes from in the experimental set-up. F is the frictional force that is present as the mass of the car is moving down the ramp at the angle of 23.96 degrees 3. Can ΔE ever be positive in this experiment? Justify your answer. No, for the ΔE to be positive, the force required to let the cart down would have to be greater than the force required to pull the cart up, which is not possible in the scenario. Seeing as the weight attached to the cart can only pull in the upwards direction, it would not be possible to have a positive ΔE. 4. What are your major sources of error? Timing, measuring mass, calculation errors. 5. Why is f a non-conservative force? Friction is a non-conservative force because it is path dependant and used in other non- conservative sources of energy 6. Should there be a variation in f for different angles of inclination? Justify your answer Yes, there should be a variation in friction based on the angle of the incline, more specifically, if the incline increases the friction should decrease. This is because the force to pull the cart up will be much
greater than the force required to let the cart down. This difference in force will lead us to see that there is less friction. Discussion During this lab, we worked in both the x and y direction with the pulling of a cart at an angle of 23.96 degrees, as we did not need to be entirely specific with whatever angle as long as we were able to pull the cart with additional weight. Our main goal was to observe the time of the cart as it was released at the top of the incline until it hit the bottom of the incline, as well as noting the height and length from the floor at both the top and bottom of the incline. Initially relapsing the cart from 23.96 degrees and using the hypotenuse from of the width and height of the incline, we timed the carts descent and the velocity was approximately 2.7791 m/s while the acceleration was approximately 0.06563 m/s 2 . Using the measurements of the mass of the car as well as the additional weight, we calculated our E 1 to be 11.4376 and our E 2 to be 10.978, this leaving ΔE to be -0.4597 and our f value to be 0.4788. This lab had a lot of room for error, when it came down to timing the descent of the cart, working out some of the values through calculations, and even possibly finding the mass of our weights incorrectly. Appendix
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