Impulse Lab

Last week, we did the impulse lab. We crashed a cart into a metal deflector to test the force created by the cart and velocity of the cart. Also, we observed the conservation of momentum within the system.

During this lab, we addressed the relationship between impulse and momentum. We found that the impulse value directly relies on the values of the final and initial momentum of the system. 

Some important equations and definitions we used today: 

1. Impulse is a change in momentum due to applied force over time
2. Impulse = final momentum - initial momentum
3. Momentum = velocity x mass

Below is a visual representation of our results: 

The graph which shows the velocity and force, and the data which shows the area and impulse of the collision is shown above. The pictures above shows that one could find the impulse, the velocities and the momentum of the system with the collected data. This is done by finding the initial and final momentum of the individual carts.

I can think of so many people who need to know about the physics of collisions for their professional lives. Just think the people who's job it is to develop car safety. For example, airbags are an excellent example of humans manipulating collisions to their benefit. First off, its a elastic collision. A lot of momentum is conserved. What this means is that the persons head will bounce off of the air bag with backwards momentum instead of most of the momentum being lost in the collision with the steering wheel. Also, the airbag increases the time of the collision which in turn decreases the force.

Collisions Lab

Last week in class we did the collision lab. We compared the conservation of momentum and energy in elastic and inelastic collisions. There was a red and a blue cart, and a motion sensor to help measure the velocity of each cart. The elastic collision resulted in the red cart colliding with the blue cart and the inelastic collision resulted in the carts sticking together with their Velcro fronts. 

Answers to the big questions: We found that elastic collisions conserve more energy than inelastic collisions do. We also calculated that momentum is more easily conserved through collisions than energy is. These patterns are shown in the picture below.

Some old and new equations and concepts we had to use today:

- Momentum = mass x force

- KE=1/2mv^2

- to calculate energy/momentum lost: final - initial divided by final x100

\We see collisions all the time but perhaps one of the most glamorous is the collision between bat and ball during a baseball game. This is an inelastic collision - neither the ball nor the bat have elastic qualities. Much of the energy from the collision travels through the bat into the hands of the batter but perhaps the most recognizable cause for the high amount of energy lost in inelastic collisions stems from the loud "crack" made when the contact occurs.

Rubber Band Cart Launcher

In this week's lab we launched a glider from a rubber band using an air track, and used a photo gate sensor to measure the velocity. We changed the distance of the rubber band being stretched for each trial. There were five trials, with the distance  from 1-5cm, or 0.1, 0.2, 0.3, 0.4, and 0.5 meters. We recorded the velocity of the cart (dependent variable) in a data table, and then repeated the experiment to get the most accurate statistics possible.

Units used:
m = meters
v = velocity
J = Jules (Energy)
K = Kinetic Energy
Us = elastic potential energy

Data:

Using the Vernier Graphical Analysis app, I created a best-fit line for all of the data we collected, using the Energy as our Y-axis, while the average of the velocity was our x-axis.

 Based on our graph, we noticed that the slope was half the mass of the cart. all of this allowed us to derive the equation for kinetic energy! KE=1/2(m)(V^2)

 In the LOL chart below, energy is transferred from elastic potential energy (rubber band) to kinetic energy (motion). When something is in motion, kinetic energy is being used. Because potential energy is transferred into kinetic energy, energy and velocity are directly proportional.

Real-World Connection: 

For example (slingshot), as the person pulls back on the slingshot, they increase the distance stretched. Therefore, there is an increase with the elastic potential energy. As the slingshot is released, the elastic potential energy is transferred into kinetic energy, which puts the ball in motion. The velocity of the ball is proportional to the kinetic energy. Therefore the more distance being pulled back on the sling, the greater the kinetic energy will be, and the faster the ball will go.