PhyslabF12_6

7/31/2019 PhyslabF12_6

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Physics and Engineering 1 Labs

Fall 2012

Instructor: Dr. Mithun Bhowmick

Laboratory Report

Lab 6: Conservation of Linear Momentum in one Dimensional Collisions

Name of student(s): Student ID(s):

1) 1)2) 2)3) 3)

Date:

Total Points Obtained:_______/100

If worked in a group and submitting one report for the entire group, mention it clearly here. If submittingseparate reports, mention that here as well.

Introduction:

In this lab you will explore the forces of interaction between two objects and study the changes in motionthat result from these interactions. The particular interest will be studying collisions, and investigatingconservation laws relating linear momentum, and (if possible) mechanical energies.

Equipment needed:

1. Pasco motion sensor (a pair)2. Smooth tracks with grooves3. Pasco cart (a set of two)4. Meter stick5. DataStudio software for recording data6. Computer with Microsoft Office loaded7. Steel blocks for adding mass to the carts

Instructions: Do NOT operate the equipment if you are not sure how to use it. Read the manual first, askquestions (or wait until you are trained) before starting the experiment. Always first click the Start buttonof the DataStudio, and then release the cart for better results.

Check with your instructor before starting. You may first want to derive the equations, and then starttaking data.

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Activity 1: Derivation of velocities in elastic and inelastic collisions (10)

a) Derive final velocities of two particles when they were subject to elastic and inelastic collisions inone dimension. Assume the two particles were traveling in the same direction before and aftercollisions. Your final expressions of the final velocity should only have initial velocities, and massesof the particles.

b) Comment on what would happen if the second particle (i.e., the one which was hit from behind)was at rest before the collision.

c) Now, define a quantity called coefficient of collision, Ω = ratio of the relative velocities of the twoparticles after and before the collision. Discuss the values of Ω for perfectly elastic and inelasticcollisions.

d) Also write down the expression for the loss of kinetic energy in case of both types of collisions.

Activity 2: Generating constant velocity graphs (10)

a) Start with one of the carts, and start graphing the position, velocity, and acceleration of it whenpushed along the track gently. Make sure that the velocity is constant (graph parallel to time axis)in each case. Generate velocities equal or close to 2 m/s, 4 m/s, -1.5 m/s, and – 3.5 m/s. Take PrintScreen of these graphs, and paste them to the Excel file for making the report.

b) Add steel blocks to the cart, one at a time, and repeat 2(a).Practice this activity until you see fairly smooth constant velocity graphs in DataStudio (DS).

Activity 3: Investigation of perfectly elastic collisions (32)

a) Take two carts (name them # 1 and #2), with no steel blocks attached. Place one of them near themiddle of the track, and the other at any of the ends. By now you are practiced in creating constantvelocity traces. Also, you should have noticed that you have two motion sensors for recording

motion of the two carts. Each time you take a data, record the constant velocities from the DS.Remember, without these velocities it will be impossible for you to analyze the experimentalresults. Keeping that in mind, create the following scenarios of elastic collisions, and generate DSgraphs for the following:-i) #1 is moving, #2 is at restii) #1 and #2 both moving in the same direction, with #1 moving slower than #2iii) #1 is moving faster than #2, in the same directioniv) #1 and #2 are moving in opposite direction (towards each other).

b) Repeat 3(a) when #1 has one steel block attached.c) Repeat 3(a) when #1 has two steel blocks attached.

d) Repeat 3(c) with #2 has one block attached.

Activity 4: Investigation of nearly inelastic collisions (32)

Observe closely the carts. You will find that they have a mechanism by which they can stick to eachother after a gentle collision. Ask your instructor, or any of the TAs for help if you are not sure. Afteryou are sure how that works, this time, generate near perfect inelastic collisions with you cartsfollowing the same route as you did in activity 3. Remember to repeat all the scenarios, as is givenin Activity 3 above. The only difference is going to be the type of collision.

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Activity 5: Analysis (16)

a) Do your recorded velocities from the measurements match with the calculated values? Youcan check this by using your derived formulae from Activity 1. Comment on yourobservations.

b) Find the kinetic energy loss in case of the inelastic collisions. Compare the measured and

calculated values. Comment on their similarity/differences.

Activity 6: Bonus Question (10)

What do you think is/are the factor(s) that could be cited as sources of errors in yourexperiments? Try to estimate the error, and from there start to propose theoretical validity of the results.

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