DOC PREVIEW
MIT 8 01 - Momentum and Collisions

This preview shows page 1-2-3 out of 9 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 9 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 9 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 9 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 9 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

MASSACHUSETTS INSTITUTE OF TECHNOLOGY Physics Department Physics 8.01T Fall Term 2004 Experiment 07: Momentum and Collisions Purpose of the Experiment: In this experiment you allow two carts to collide on a level track and run into a spring that is attached to a force sensor. You will measure the position and velocity of the first cart and the force exerted by the spring while it is compressed. You can analyze your data to determine the following things from this experiment: • An experimental test of the conservation of momentum in elastic and inelastic collisions. • Determination of the maximum kinetic energy that is available to do non-conservative work in a completely inelastic collision. • You will make use of most of the ideas and computational tools that we need to analyze collisions in one dimension. Because the track is level, we do not need to consider changes in the gravitational PE of the carts and may take it to be zero. If we consider the two carts to be an isolated system (this is a good approximation so long as the friction forces are small), the only mechanical energy is kinetic, K. A collision is inelastic if some of the initial K is used to do non-conservative work. It is elastic if no K is “lost.” The collision is c ompletely inelastic if the maximum amount of K (consistent with conservation of momentum) is converted to non-conservative work; usually that is what people mean when they refer simply to inelastic collisions and it happens when the two colliding objects stick together. Setting Up the Experiment: A Byx• At the the end of the track with the level adjustment screw attach a force sensor with the hook replaced by the lighter of the two springs. • Clip the the motion sensor to the other end of the track. • Level your track as well as you can using the level adjustment screw. Test by making sure an empty cart does not have a tendency to roll in either direction; the test is more sensitive if you put two 250 gm weights in the cart. Experiment 07 1 November 3, 2004Setting up DataStudio: Connect the force sensor and set it to a • 500 Hz sample rate with low sensitivity. Tare the sensor when nothing is in contact with the spring. Connect the motion sensor and calibrate • it. Choose the trigger rate to be 80, and set it to measure position and velocity (acceleration is optional). • Set the sampling options for Delayed Start to “position rises above 0.3m” and do not keep any data prior to the start. Set Automatic Stop to “position falls below 0.3m.” Create graphs to plot force, position and velocity as a function of time by dragging entries from the Data window onto the Graph icon in the Displays window. Inelastic Collisions: You should study inelastic collisions first in this experiment. Place two empty carts on the track with the the Velcro pads facing each other. One cart (which I call the target cart, with mass mB ) should b e placed on the track with the end with the Velcro pads about 70 cm from the motion sensor; then the other end of the cart will be about 10 cm from the spring on the force sensor. The second cart (which I will call the incident cart, with mass mA) should be placed on the track between 16 cm and 20 cm from the motion sensor. You should push the incident cart just hard enough that it comes back to the starting point after colliding with the other cart and bouncing off the spring. If you push it too hard it may jump during the collision with the target cart, and if you push it too softly it will not come back far enough to stop DataStudio from taking data. Experiment 07 2 November 3, 2004You should experiment to get this right before you start to make measurements. How hard you need push it changes with the masses of the two carts and whether or not the collision is inelastic, so you will have to find this out for each of the six measurements that you make To make a measurement, click the DataStudio start button and start the incident cart rolling towards the target. The cart will roll at least 10 cm before data are recorded; that gives it time to stabilize and roll smoothly after you push it. Make measurements with mA = mB = 250 gm (both carts empty), mA = 250 gm, mB = 500 gm, and mA = 500 gm, mB = 250 gm. Measure vA,1 before the carts collide and v2 = vA,2 = vB,2 after the collision when the two carts are stuck together but have not yet hit the spring. (Notation: the subscripts A and B refer to the carts, and subscripts 1 and 2 are before and after the carts collide, respectively.) My results are in the two graphs below. Position vs. Time Velocity vs. Time The best way to measure vA,1 is to select the velocity data before the collision and use the statistics tool (Σ) on the graph to find the average—as shown on the graph below. Then select the data after the collision (but before the cart hits the spring) to measure v2. You will not nee d the force sensor data for the inelastic collisions. Record the values of vA,1 and v2 for each col-lision in the table below. mA mB vA,1 (m/s) v2 (m/s) 0.25 kg 0.25 kg 0.25 kg 0.50 kg 0.50 kg 0.25 kg Experiment 07 3 November 3, 2004Elastic Collisions: These measurements will be done exactly like the preceding ones except the carts are placed on the track with the opposite ends (the ones containing magnets) facing each other. Then the collision between the carts will be elastic. You should measure collisions with mA = mB = 250 gm (both carts empty), mA = 250 gm, mB = 750 gm, and mA = 750 gm, mB = 250 gm. Measure vA,1 (before) and vA,2 (after the carts collide, but before the target cart bounces back to hit the incident cart). The motion sensor can only measure the velocity of the incident cart. You know the initial velocity of the target cart, vB,1, is zero, and you can find vB,2 after the collision from the impulse given to the target cart by the spring. Here is how to do it. 1. Use a combination of selecting points and the “Scale to Fit” button at the left of the graph’s toolbar to expand the force graph to show only the time around the collision of the target cart with the spring, like this 2. Open the pull-down menu next to the Σ on the graph’s tool bar. Check the “Area” item at the bottom of the menu. Uncheck the other items. 3. Select the data points that correspond to the collision (F > 0) and click the Σ


View Full Document

MIT 8 01 - Momentum and Collisions

Documents in this Course
Load more
Download Momentum and Collisions
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Momentum and Collisions and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Momentum and Collisions 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?