Lab10 - Collision PDF

Preview

Summary

Lab report...

Description

IUPUI Physics Department

21800/P201 Laboratory

Elastic and Inelastic Collisions Objectives In this lab you will  

test the Laws of Conservation of Momentum and Energy as they apply to one and twodimensional collisions. use the Exploration of PHET collision lab to simulate the collision of two pucks.

Equipment https://phet.colorado.edu/en/simulation/legacy/collision-lab

Theory The (linear) momentum of an object of mass m moving with velocity v is given by p = mv. If there is more that one object present in the system, the total (linear) momentum is simply equals the vector sum of the individual momenta: m1v1 + m2v2 +… The total mechanical energy of the system is the scalar sum of the individual energies: E1 + E2 +… The Law of Conservation of Linear Momentum states that the total linear momentum of a system of objects is conserved only if the net external force acting on the system is zero. The Law of Conservation of Mechanical Energy states that the total mechanical energy E is conserved only if there are no non-conservative forces acting on the system. Specifically, in a system consisting of two objects of momenta pred and pblue, the Law of Conservation of Linear Momentum may be expressed as ( pred + pblue)i = (pred + pblue)f where subscript i indicates the initial value and f indicates the final value of the total momentum. Similarly, the Law of Conservation of Mechanical Energy may be expressed as (Kred + Kblue)i = (Kred + Kblue)f where we have assumed that only the kinetic energy changes in the system. Elastic collisions conserve both momentum and energy; inelastic collisions conserve only momentum.

Procedure Set-Up and Data Collection 1) Go to https://phet.colorado.edu/en/simulation/legacy/collision-lab on your computer. Familiarize yourself with the software. For 2-D push advanced tab in the top left. Press Show values checkbox to see all data or press more Data. 2) The masses of the pucks can be changed by adjusting the two slide bars at the top of the left column (see Figure 1 below). To move a particular puck, right click on it and drag it wherever you wish. To change its initial velocity, click on its initial velocity arrow and stretch it to make a larger velocity. 3) The “Elasticity” slide bar determines how elastic you wish to make the collision: 0 = perfectly inelastic and 1 = perfectly elastic. 4) If you wish to view the full trail of the collision in pause mode, check the circle “Show Paths” Checkbox in the advanced tab.

Page 1

IUPUI Physics Department

21800/P201 Laboratory

5) To run the simulation, click on “Play.” Use “Pause” button to restart from the beginning. 6) “Pause” whenever you want to record data after the collision. Note that the x-component of velocity is positive (+) whenever the mass moves to the right and the y-component is (+) whenever it moves upward. Otherwise these two components are (–). Be sure to record the signs in your data tables. Remember kenetic energy of an object is Ek= ½ mv2

Figure 1

Page 2

IUPUI Physics Department

21800/P201 Laboratory

Data Sheet – Elastic and Inelastic Collisions Name: Chesney McIlrath Date: 11/18/20

Case 1: Elastic Head-on, Equal Masses, Stationary Target (Green) Set massred = massgreen = 5 kg

Coefficient of restitution = 1 Initial

Red Green Total

Final

velocity

momentum

kinetic en.

.4 m/s 0 0.4

0 2 kg m/s 2

0.40J 0 0.4

velocity

momentum

0 0 0.4 m/s 2 kg m/s 0.4 2

kinetic en.

0 0.40 J 0.4

Is the total velocity conserved in this case? Explain your answer. Yes because it’s just transferred.

Is the total momentum conserved in this case? Explain your answer. Yes because the red ball is zero and once it pushes the green ball the green ball has momentum.

Is the total kinetic energy conserved in this case? Explain your answer. Yes because the red ball is the one with the KE initially then it transfers to the green ball.

Page 3

IUPUI Physics Department

21800/P201 Laboratory

Case 2: Inelastic Head-on, Equal Masses, Stationary Target (Green) Set massred = massgreen = 5 kg

Coefficient of restitution = 0

velocity

Initial momentum

kinetic en.

velocity

.4 m/s

2 kg m/s

0.40 J

0.2

Green

0

0

0

0.2

Total

0.4

2

0.4

0.4

Red

Final momentum

2.5 kg m/s 2.5 kgm/s 5

kinetic en.

0.2 0.2 0.4

Is the total velocity conserved in this case? Explain your answer. Yes because the velocity from the red ball is able to move the green ball.

Is the total momentum conserved in this case? Explain your answer. Yes because initially the red ball has all the momentum then some of it is moved to the green ball so both balls have a momentum of 1 kg m/s.

Is the total kinetic energy conserved in this case? Explain your answer. Yes because energy cannot be created nor destroyed, only transferred.

Case 3: Elastic Head-on, Unequal Masses, Stationary Target (Green) Set massred = .1 kg, massgreen = 10 kg velocity Red

Green

.5 m/s 0

Initial momentum

0.1 kg m/s 0

Coefficient of restitution = 1 kinetic en.

velocity

Final momentum

0.05 J

-0.98 m/s -0.02

-0.10 kg m/s 0.2 kg

0 Page 4

kinetic en.

0.048 0.002

IUPUI Physics Department

Total

0.5

21800/P201 Laboratory

0.1

0.05

m/s -1

m/s -0.8

0.05

Is the total velocity conserved in this case? Explain your answer. Yes because the velocity of the red ball is unable to move the green ball so the velocity of the red ball remains and the velocity of the green ball is zero.

Is the total momentum conserved in this case? Explain your answer. Momentum is lost because once the red ball hits the green ball it bounces backwards which gives it a negative momentum Is the total kinetic energy conserved in this case? Explain your answer. Yes because energy is transferred, not created or destroyed.

Case 4: Elastic Head-on, Unequal Masses, Stationary Target (Green) Set massred = 5 kg, massgreen = 10 kg

Coefficient of restitution = 1

velocity

Initial momentum

kinetic en.

velocity

Final momentum

.4 m/s

5 kg m/s

2.5 J

Green

0

0

0

Total

0.4

5

2.5

-0.33 m/s 0.67 m/s 0.34

-1.67 kg m/s 6.67 kg m/s 5

Red

Is the total velocity conserved in this case? Explain your answer. No some of it is lost because when the red ball rolls back it is slower.

Is the total momentum conserved in this case? Explain your answer. Yes because the red ball rolls back after hitting the green ball. Is the total kinetic energy conserved in this case? Explain your answer. Page 5

kinetic en.

0J 2.5 J 2.5

IUPUI Physics Department

21800/P201 Laboratory

Yes because energy cannot be created nor destroyed.

Case 5: Elastic Head-on, Equal Masses, Moving Target (Green) Set massred = massgreen = 5 kg

Red Green Total

Coefficient of restitution = 1

velocity

Initial momentum

kinetic en.

velocity

Final momentum

kinetic en.

.4 m/s -.2 m/s 0.2

5 kg m/s 0 5

2.5 J 0 2.5

0 1 m/s 1

0 5 kg m/s 5

0 2.5 J 2.5

Is the total velocity conserved in this case? Explain your answer. No it increases once the red ball hits the green ball because the green ball started moving from rest.

Is the total momentum conserved in this case? Explain your answer. Yes since the balls are of equal mass.

Is the total kinetic energy conserved in this case? Explain your answer. Yes because energy cannot be created nor destroyed.

Page 6

IUPUI Physics Department

21800/P201 Laboratory

Figure 2 Case 6: 2-d Elastic Head-on, Equal Masses, Moving Target Set up the pucks as shown in Figure 2.

Set massred = massgreen = 5 kg

Coefficient of restitution = 1

Initial Data: X-velocity

Y-velocity

X-momentum

Y-momentum

Kinetic energy

.4 m/s

0

0

0.04 J

Green

0

.2 m/s

0.203 kg m/s 0

0.02 J

Total

0.4

0.2

0.203

0.13 kg m/s 0.13

X-velocity

Y-velocity

X-momentum

Y-momentum

Kinetic energy

0.007 kg

-0.01 kg

0.02 J

Red

0.06

Final Data: Red

0.014 m/s -0.02 m/s

Page 7

IUPUI Physics Department

21800/P201 Laboratory

Green

0.392 m/s

0.28 m/s

Total

0.406

0.26

m/s 0.196 kg m/s 0.203

Is the total x momentum conserved in this case? Explain your answer. Yes because the masses are the same size.

Is the total y momentum conserved in this case? Explain your answer. Yes because the masses are the same size.

Is the total kinetic energy conserved in this case? Explain your answer. Energy cannot be created not destroyed.

Page 8

m/s 0.14 kg m/s 0.13

0.04 J 0.06...