Group member names: -Greg Strickler Laboratory Activity 4: Forces -Chris marino -Won-Yong.Shin
Objectives Explore how force is related to acceleration and velocity. Explore behavior of force sensors.
Equipment Dynamics cart Force sensor Track for cart 2 USB Links Cart masses Motion detector Spring scales USB hub
Activity One: Spring pull Prediction 1: You will place the cart on the track, place the cart masses on it, and attach a spring scale. You will then pull the cart with a constant force. How will the cart move? It will move with a constant velocity.
Experiment 1: Make sure your spring scales are zeroed when horizontal (most adjust by sliding the metal plate on front.) Then hook one on the cart and pull it, trying to keep the force about 0.5 N the whole time. You may have to practice several time to be able to maintain an approximately constant force on the scale. Question 1: How did the result compare to your prediction? Explain how the cart moved (its velocity, acceleration, etc.). Had constant velocity and no acceleration. Question 2: Hook a second spring scale on the cart. (One way is to use the magnetic “bumpers” to grab the steel hooks of the scales.) Pull both of them with a force of about 0.5 N. How does the motion compare to the first case? The cart appears to have twice the velocity as before, and still no acceleration.
Question 3: Hook the two spring scales to opposite sides of the cart and pull on both with the same force. a second spring scale on the cart. Pull both of them with the same force. How does the car move? Note: there are TWO ways the cart may move (or not) in this case. If you can’t find both of them, ask for help. In the first case the cart didn’t move. But if both spring scales are pulling the same amount and moving in the same direction the cart will move in that direction at the same velocity.
Activity Two: Calibration of force sensors Experiment 1: Connect the force sensor to the computer by attaching it to the USB link and attaching that to the back of the computer like you did with motion sensors. Start up Data Studio when the option comes up. Once that is running, double-click on the “Digits” in the “Displays” panel (lower half of left-hand side). Zero the force sensor by pressing the small “Zero” button on it. (It is very important that you always press this button with nothing on the hook before taking any data measurements, since the zeroing can drift rapidly with these sensors.) Have one member of your group hold the force sensor while the other hooks the spring scale on to it and pulls with a force of 1.0 N. Start taking data and record the force sensor value in the chart below. Repeat for 2.0 N, 3.0 N, 4.0 N and 5.0 N. If you are not sure that this is working properly, check with your instructor. Spring Scale (N) Force Sensor(N) 0.0 N 0N 1.0 N -1N 2.0 N -2N 3.0 N -3N 4.0 N -4N 5.0 N -5N Question 4: How does the force measured by spring scale compare to that measured by the force sensor? Can you trust the force sensor to tell you the same thing as the spring scale would? What must you constantly do to ensure that the measurement is accurate? There opposites, because we are pulling on the detector instead of pushing on it. You must zero the detector each time before taking measurements.
Activity Three: Force and motion Experiment 3: Attach the force sensor to the cart using the screw, placing it into the hole labeled “cart” and not the one labeled “IDL.” Plug both sensors into the USB bus and then the bus into the computer, and connect power to the USB bus. Place the motion sensor on one end of the track, with the cart in the middle with the force sensor on the opposite side of the cart. Make sure no cables get in the way of the motion sensor, and that it is on the “cart” setting. Open the file xxxx in DataStudio. Have one member grasp the hook on the force sensor while data is taken and move the cart back and forth, both quickly and slowly. Paste the resulting graph below.
Question 5: Which motion graph, velocity or acceleration most closely resembles the force graph? Are the values equal, or are they proportional? The acceleration and the force are proportional to each other.
Summary The following questions will help you get the main ideas out of this lab. You should find these straightforward questions, but take the time to talk it over with your team and write complete answers to these questions. You may find your answers here to be the most useful part of this lab down the road. Summary 1: Is force proportional to velocity or to acceleration? Its proportional to the acceleration graph.
Summary 2: If more than one force is applied to an object, what is the acceleration proportional to? Can you simply add the magnitudes of the forces? If not, what must you do? The acceleration is proportional to the sum of the two forces if there applied from the same direction, if there on opposite directions you must take the difference of the forces. Summary 3: What evidence do you have to back up your previous two statements? By experiments ran in the datastudio proves that our answers are correct.