EF151 Final Project

Team B1-5

12/21/2018

The Grand Salute

Introduction:

We set up a series of four energy transfers in order to raise the American flag. The first two transfers we used ballistic objects and the force of gravity to transmit energy. The third ballistic object falls onto a see-saw and transfers its energy to a car on a track which used the initial push and gravity to make it to the end of the device. This sets off a mouse trap which raises the flag.

Design Process:

First we brainstormed ideas for energy transfers. During the session we generated many ideas of what the structure will generally look like in the end. At first we didn’t really think about the materials, just the display. After we had the basic idea of the structure we discussed the materials we would need to bring our ideas to fruition. Matt had the general idea of how everything will work and he drew a design of it on a board. We discussed every aspect of the structure such as what could go wrong and what would be the best method to approach building that part of the device. After all this we finally discussed the materials we would need to complete the initial design all the while keeping mindful of the cost of materials in order to not exceed the budget. The next day we met up and went to Lowes, though we had intended to go to Home Depot. We opted to go to Lowes because it had less expensive, but higher quality items. We basically wandered around aimlesslylooking for items that would fit the mold of our project. We found the majority of our items from Lowes which included the main base of the structure. The few other materials were items found around the house, such as a golf ball.

Construction Process:

After we returned from Lowes we began construction in Estabrook room 13. We sawed all the garden stakes to fit the various sizes we needed for the structure. We used these stakes as pillars to secure other objects. It helped hold the utility pipe up, which is the initial object the first ball goes through. They also help hold up the pulley system which initially wouldn’t have worked if we hadn’t added these stakes as a support system. The stakes also hold the cup that tips over from the weight of the ball falling into the first cup that is attached to the pulley system. The cup that tips over to release the second ball was initially a failure. To fix this we added stakes on both sides of the cup and put nails through the cup to hold it in place. Then we put the string at the bottom of the cup which would be pulled and tip the cup when the first ball falls into the first cup. Then a series of four stakes were made to make a table like object. The table was hollow in the middle with a small PVC pipe in the center held up by nails. A cloth is placed over this table. A third ball is resting on the far side of the table. The second ball drops onto the cloth from the cup pulley system and launches the third ball down the cloth ramp. The third ball goes down the large PVC pipe with a foam cup attached to the top for a better chance of the ball making into the hole. The ball still missed often, so we added a wall structure to guide the ping pong ball into the hole. The ball goes through the PVC pipe and is guided into a half foam cup connected to a see-saw. The weight of the ping pong ball pushes the other end of the see-saw up which hits the tail end of the car and starts it moving along the track. Gravity and height of the track helps it gain momentum down the track to get to the final apparatus.The final apparatus is a stick attached to a string which is attached to the mouse trap. Another string is attached to the snapping part of the mouse trap and the flag that is raised.

Calculations:

First we calculated the tension of the string on the pulley system. Since it was in equilibrium it was the weight of the cup and the ball in the cup to keep it in equilibrium. Hence, we multiply the mass of these objects by gravity:

0.024 kg*9.81m/s^2=0.235 N

We then calculated the theoretical velocity of the ball right before the collision with the cup. We used Conservation of Energy. We assumed it didn’t lose any mass from the drop to before the collision:

V= sqrt(2*9.81m/s^2*0.348m)=2.61m/s

We found this was enough to overcome the equilibrium of the tension.

We than calculated the velocity of the car at the bottom of the track using Conservation of Energy. We assumed no energy loss from the bottom to the point of the inelastic collision with the stick:

V=sqrt(2*9.81m/s^2*0.133m)=1.62m/s

The velocity and mass of the car gave it enough momentum in the inelastic collision with the stick to overcome the string that is holding the mousetrap.

Bill of Materials:

Wood Base 15/32’’X 2’ X 4’ / $8.97
Wood Stakes 5’ / $3.00
Utility Pulley 2 ½’’ / $2.50
PVC Pipe ½’’ / $0.20
PVC 2’’ 45° Bent / $3.14
Nails / $0.05
Styrofoam Cups / $0.10
Toy Sport Ball (Football) / $0.25
Ping Pong Ball / $0.50
Golf Ball / $0.85
Curtain Tie / $0.40
Small American Flag / $0.75
Hot Wheel Car and Track / $3.50
Mouse Trap / $0.50
String / $0.02
Binder Clip / $0.19
Wooden Clip / $0.08
Total / $25.00

Conclusion:

The team was successful in building the device. We learned that the initial design may have to be modified in order for a process to work out in the end. Also that critical thinking along the process of designing and building of the structure is required in order to get around problems that stop us from our objective. Our main problem was getting around everyone’s schedules so that we could all work together. In the end we had enough time to get around this problem. We ran into some problems with our original design, but with some great critical thinking (from Matt) we got the project done successfully. The main thing we would do differently is initiate the project little earlier than we did. We finished the project quite nicely, but if it didn’t turn out so smoothly we could have potentially failed to obtain our objective.

References:

We used a couple of ideas from the video Betsy shared with us at:

Mainly we communicated with other students doing the same project and asked what they thought of each part of our device. However, Matt came up with most of the ideas just by thinking about it during our brainstorming session.