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Physics Bridge Project

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on 16 January 2014

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Transcript of Physics Bridge Project

Physics Bridge Project
First Lab : Brick's Velocity v. Angle
First Approach
-Measured mass of brick and attached string to the body of the brick

-Pulled brick with Newton meter until the brick passes the line drawn in chalk.

-Measured the newtons and massed the objects used to get different angles
Realized we were measuring
static friction
so we needed a new approach

Second Approach
-Used Brick that had already been measured
-Tied string to the brick and drew a chalk line on table 6in long
-Duct taped the string to the bottom of the brick for a better angle measurement
-Moved the brick from point A to point B (the 6in) while measuring the average newtons
Bridge App
All of us worked to complete as many levels:
Approaches that worked:
-If both sides were symmetrical
-Stronger materials i.e. cement and steel cables
-Stable structure supported in the middle

Greater Angle = Less Tension
Center of Gravity
Center of Mass
Point at which all of the weight of an object appears to be concentrated
“Center of rotation”
motion of any object through space in terms of the translation of the center of gravity of the object from one place to another
rotation of the object about its center of gravity if it is free to rotate
Can describe the...
an average of the masses in a system factored by their distances from a reference point
(Different equations for a continuous distribution of mass and mass distribution of particles)
Andrew, Elise, Morgan, Mike
Period 2
Elise and Morgan
Golden Gate Bridge
Strauss Hybrid Concept
Chesapeake Bay Bridge
Beam and Tunnel method
Verrazano-Narrows Bridge
Double Deck Suspension Bridge
used in a uniform gravity field to... describe the
point in a system
which describes the
system’s response
external forces and torques
In a uniform gravitational field, the center of mass and the center of gravity are synonymous.
Both refer to points on/in a system
Center of mass:

a geometrical measurement not considering the weight distribution
one location on a particular mass structure where the distribution of weight is the same no matter the direction of the measurement as it pertains to that one particular mass structure.

Failed attempt
Weak support and materials
Measured angle
We were measuring
the weight parallel to the table
Second Lab: Force Addition Lab
Third Lab: Tension Lab
Center of Gravity & Mass Experiments
and the
Dollar Bill
Center of Gravity
of a
Regular Shaped Object
Center of Gravity
of an
Irregular Shaped Object
Equilibrium Game
Balance a can filled with water
Balance a can filled 1/3 with water
What happens?
What concepts justify the outcome/observation?
How would you improvise the system?
Balance quarter on a dollar bill for 10 seconds min
Our strategy and successes:
Is it fascinating?
Twist clockwise and anticlockwise. Observe.
Improvise the design to make it spin both ways.
What made the design work?
Physics connection:
Where do we see this design very essential in real life?
On a wooden block narrow edge hang the wooden blocks
Physics Connection:
Take a piece of folder and cut into any regular shape.
Find the center of gravity by drawing lines of forces.
Test the point where Fnet = 0
Take a piece of folder and cut any irregular shape.
Find the center of gravity by drawing lines of forces.
Where is c.g. in giraffe?
How does the center of gravity and equilibrium apply to the bridge?
Where is the center of mass and center of gravity?
What is the difference between center of mass and center of gravity?
Center of gravity:
Andrew's Diagram
Morgan's Diagram
Mike's Diagram
Elise's Diagram
Fopp = 7.5 N Fadj = 8 N Fr = 11 N
Fopp = 4.5 N Fadj = 5 N Fr = 6.7 N
Fopp = 2.5 N Fadj = 4 N Fr = 4.72 N
Fopp = 6 N Fadj = 8 N Fopp = 6N
Forces on String Lab
Angle theta and tension have an inverse relationship, so when the
angle increases
tension decreases

T=(mg/2)(csc theta)
the app game
-One main string attached to another string to create an angle

-Three Newton meters attached to each end

-Completed four extra examples with different angles and forces using string and Newton meters

-Each individual created a force diagram
In order for the
of forces/vectors to follow the
hypotenuse theorem
, the outside forces have to be
Ex. 8N^2 + 6N^2 = 100N
square root of 100 = 10 N
-One main string attached to another string to create an angle

-Three Newton meters attached to each end

-Completed given sum of forces problem as a goup

-Created four extra examples with different angles and forces using string and Newton meters

-Each individual created a force diagram
Fnet = 0
Forces balanced
Clear can (mark fluid locations)
Plumb line the can
Dollar bill is a little bent
One hand
Fnet = 0
Apply force at both ends
Shift center of mass
Add tape to the thinner side in order to make the object level
-Plumb line
-Find centers
-Make toothpick
under center
What evidence/s can you find to support the features of the game?
Balancing, by distributing weight and outer forces
Data Collection
Our Design
Center of Mass:
Between the two forks
Center of Gravity:
Same as CM
Equilibrium, center of mass, center of gravity
Almost in the middle of it's stomach but closer to the front.
This is why the giraffe can slide down and not tip over.
In order for a bridge to stay in place, all the forces acting on the bridge must add up to produce zero net force.
What physicists call any situation where the net force is zero.

The concept of equilibrium is important to the design of
, and virtually every
(like video games)
ever invented by humans.
Building Bridges
Experiment 1:

When a beam bends, the molecules of the upper part compress and the molecules on the underside are in tension.

The middle section on the beam in in a neutral state, neither compressed or strained, so it can be removed to make the beam lighter.

Concrete is the most reliable material due to its compressive strength, unfortunately it is weak when in tension.

In order to make it stronger, it is possible to reinforce the concrete with steel bars on the inside.

There is a
relationship between
and the amount of
added to the ruler. As the weight increased by 50g the tension increased by .5N
Testing Girders

Of all the shapes, the triangle was the strongest and most rigid. The more space there is in between the structure, the less stable the shape becomes.

Cut straws into thirds and glue them together using a hot glue gun.

Set up metal bars and hang a ruler from two newton meters.

Measure tension using weights hung from the ruler in increments of 50g.
Andrew's Luggage Data
Morgan's Luggage Data
Mike's Luggage Data
Elise's Luggage Data
Law of Moments
Our Bridge Problem & Solution
Building a Beam
Experiment 2:
Experiment 3:
Building a Girder Bridge
Competition 1
Experiment 4:
Building a Girder Bridge
Competition 2
Cracks under tension
Steel rods
Re-inforced concrete beam
Use girders to build a bridge to cross a 10 cm gap.
20 cm
90 degree
(Later on in the experiment, we moved the gap to be 10 cm)
Data Collection
Features of the Game
When we
the can with
the can, the
center of mass
changed to the
of the
, rather than the middle of the can.

Because of the
change of mass
overall, the
center of gravity changed
as well, resulting in the center of gravity being in the
of the can. This change allowed for the can to balance on its side.
Center of Mass and Center of Gravity
Color Block Codes
these must be tapped in order to get rid of them
these colored blocks must be left in the end to balance
Forces and Center of Gravity and Mass
Forces of Coin and Dollar Bill
Twister Lab Process
Center of Gravity of Irregular shaped object- process
Features of Equilibrium
Morgan & Elise
When all forces that act upon an object are balanced.
If the rightward forces are balanced by the leftward forces and the upward forces are balanced by the downward forces, then it is balanced.
Does not mean all forces
are equal to each other.
Fnet = 0 N
Acceleration = 0 m/s^2
An object at equilibrium is either:
at rest and staying at rest
in motion and continuing in motion with the same speed and direction.
Assessment of Block app
Physics of balance and weight shift, newtons third law, equilibrium, and concept of forces
Changes and Additions:
- Visual of present forces for each level
- Brief explanation of forces being used
- Tie together more reactions; change of mass/gravity/position
-Option to work under different weather conditions; rain/wind/heat
- Option to use different materials
-More colors to create complexity
-Provide physics related hints to move game along
-Have level where player can create original structure
Physics Aspect:
Height (m)
Arm Length (m)
Angle between arm and suitcase handle- most comfortable
Height of bag w/ and w/o handle (m)
Depth of bag (m)
Width of bag (m)
Center of gravity
is in the center
F1D1 does not equal F2D2
Which is why we added the tape
Center of Mass
Center of Gravity
Girder Bridge Research
1 balsa wood strip
Model Ratio
Max Load (N)
Weight of Bridge (N)
Our Design
Bendorf Bridge
Rhine River
Google Sketchup
Conclusion before final design...
To maximize carrying capacity
Rectilinear Design
you need a
yields the greatest internal volume
Rectilinear Configuration
moment you introduce curved sides or edges, you begin to lose storage space.
makes bag appear more aerodynamic...
adding external pouches
a bag's
without adding appropriate corresponding
storage volume
but it's really not.
Although they have
identical external dimensions
the rectilinear bag offers an astonishing
29% more storage space
Three Problems
with non-rectilinearity
2. Extending bag at its front (to the right in this photo) moves its
center of gravity
further from one's body than it need be, making it less comfortable to carry
1. More awkward to maneuvre in crowded situations
3. Curved sides = more difficult to pack effectively
Taller the person, smaller the degree of angle between arm and suitcase handle
2 wheels
.50 m avg height suitcase
Rectilinear Design
1.7 avg person height
60 degree avg angle (most comfortable)
.60 m avg handle height
Side View
Front View
.60 m
.50 m
Avg human height
2 wheels
Donghai Bridge
South China Sea
What our bridge looks like...
Keeping in mind...
contained by, consisting of, or moving in a straight line or lines
8.11 total strips of balsa wood
Bridge Structure Weight
209 g = .209 kg
Wt (N) = mg
Wt (N) = (.209 kg)(9.8 m/s^)
Wt = 2.0482 N
Max Load Weight
393 g = .393 kg
Max Load Weight
30 lb total added weight
30 lb = 13.6078 kg
Total Max Load Weight
.393 kg + 13.6078 = 14.0008 kg
Wt (N) = mg
Wt (N) = (14.0008)(9.8)
Wt = 137.208 N
Model Ratio
Max load (N)
Weight bridge (N)
137.208 N
2.0482 N
= 66.9896 N
What we should have done....
-Need more structural support

-Additions would increase support and strength of design
The End
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