Lab 6: Collisions in One Dimension
PHY 111/211
Lab 8: Collisions
Objectives:
- Investigate different type of collisions
- Determine if the total momentum and energy is conserved in each type of collision.
Introduction:
Newton’s second law is written with the formula , where
is the net external force acting on the system during the collision and
is the net momentum of the system. This momentum is given to an object by its mass, m, multiplied by its velocity, v;
, which is a vector quantity. If
, then
, which means P = constant. Therefore, when two objects collide on a horizontal surface devoid of friction, the total force acting on the system during the collision is equal to zero which means that
where is the vector sum of the moment of the two objects before the collision and
is Vector sum of the moment of the two objects after collision. Expanding the conservation of momentum equation for two-body collision, we get
There are two types of collisions:
- Elastic Collision: In this collision the total kinetic energy before collision equals the total kinetic energy after collision.
- Inelastic Collision: In which there is a loss in kinetic energy so the total kinetic energy before collision does not equals the total kinetic energy after collision.
Procedure:
In this experiment, we will be using the Phet Simulation. Open the link: https://phet.colorado.edu/sims/html/collision-lab/latest/collision-lab_en.html and select the intro tab.
Part 1: Elastic Collision (same mass)
In this collision, set the mass of the two objects to 2 kg.
- To make the collision elastic drag the slider of Elasticity to the right 100%.
- Click on more data.
- Change the values as listed in the table. To change any value in the table by click on it then type:
| Object | Mass (kg) | Position (m) | Initial velocity (m/s) |
| Mass 1 (blue ball) | |||
| Mass 2 (pink ball) |
- Click on play, then pause after collision.
- Record the values of final velocities.
- Calculate the
,
and record them in the table. Remember
.
- Repeat for a
| system | |||||||||
- State your observations and any calculations. Include answer to the questions listed below in your observations.
Observations:
Questions:
- Is the total momentum of the system conserved? Is the momentum of each cart conserved?
- Is the total kinetic energy conserved?
Part 2: Elastic Collision (different mass)
- Keep Elasticity to 100%.
- Change the values as listed in the table. To change any value in the table by click on it then type:
| Object | Mass (kg) | Position (m) | Initial velocity (m/s) |
| Mass 1 (blue ball) | |||
| Mass 2 (pink ball) |
- Click on play, then pause after collision. Record the values of final velocities.
- Calculate the
,
and record them in the table. Remember
.
| system | |||||||||
- State your observations and show sample calculations. Include answer to the questions listed below in your observations.
Observations:
Questions:
- Is the total momentum of the system conserved?
- Is the total kinetic energy conserved?
Part 3: Inelastic Collision
- Change the Elasticity to the 40%.
- Change the values as listed in the table. To change any value in the table by click on it then type:
| Object | Mass (kg) | Position (m) | Initial velocity (m/s) |
| Mass 1 (blue ball) | |||
| Mass 2 (pink ball) |
- Click on play, then pause after collision. Record the values of final velocities.
- Calculate the
,
and record them in the table. Remember
.
| system | |||||||||
- State your observations. Include answer to the questions below in your observations.
Observations:
Questions:
- Is the total momentum of the system conserved? Is the momentum of each cart conserved?
.
- Is the total kinetic energy conserved?
Part 4: Perfectly Inelastic Collision
- Change the Elasticity to the 0%.
- Change the values as listed in the table. To change any value in the table by click on it then type:
| Object | Mass (kg) | Position (m) | Initial velocity (m/s) |
| Mass 1 (blue ball) | |||
| Mass 2 (pink ball) |
- Click on play, then pause after collision. Record the values of final velocities.
- Calculate the
,
and record them in the table. Remember
.
| system | |||||||||
- State your observations. Include answer to the questions listed below in your observations.
Observations:
Questions:
- Is the total momentum of the system conserved? Is the momentum of each cart conserved?
- Is the total kinetic energy conserved?
