Definitions
Define force
A push or a pull
What is the equation for force?
F=m*a
When offensive lineman Aaron Gibson reported to the Buffalo Bills in 2006, he was the largest NFL player ever and had a mass of 186 kg. What was Aaron’s weight in newtons?
w=mg = 186kg(9.81m/s2)=1825 N
A mathematical representation of anything that is defined by its size or magnitude and its direction
This is the only mammal that can truly fly.
Bat
What are colinear and concurrent forces?
Colinear=forces that have the same line of action
concurrent=forces that do not act along the same line of action on an object but act through same point
Pythagorean theorem
a2+b2=c2
The coefficient of static friction between Jimmy’s hand and his tennis racket is 0.45. How hard must he squeeze the racket (what is R?) if he wants to exert a total force of 200 N along the longitudinal axis of the racket?
Us=0.45
Fs=200N
R=?
Fs=Us(R)
R=200N/0.45=444N
9.81 m/s2
acceleration due to gravity
This animal's heart beats between 250 and 1,200 times per minute during the day.
Hummingbird
Define internal and external forces, using a human body give examples of each.
Internal forces=forces acting within a system or object whose motion is being investigated
External forces=forces acting on an object as a result of its interaction with the environment
Ex: muscles/bone/connective tissue in human body (internal), something pushing or pulling a human (external)
Solving for the hypotenuse when you know the opposite component of force and the angle
sin(theta)=opposite/hypotenuse
Veronica is working in a shoe test lab measuring the coefficient of friction for tennis shoes on a variety of surfaces. The shoes are pushed against the surface with a force of 400 N, and a sample of the surface material is then pulled out from under the shoe by a machine. The machine pulls with a force of 300 N before the material begins to slide. When the material is sliding, the machine has to pull with a force of only 200 N to keep the material moving.
R=400N
Fs=300N
Fd=200N
---Us?
Fs=Us(R)
Us=Fs/R=200N/400N=0.50
---Ud?
Ud=Fd/R=200N/400N=0.50
Forces that occur between objects in contact with each other
Contact forces
This is the longest river in the world, located in Africa.
The nile
What is tensile and compressive force?
Tensile=internal pulling forces
Compressive=internal pushing forces
Solving for an angle when you know the adjacent and hypotenuse components of force
theta=arccos(adjacent/hypotenuse)
Katie pulls upward with a 400 N force on a 700 N barbell that is resting on the floor. The barbell does not move. How large is the normal contact force exerted by the floor on the barbell?
Sum of forces=0
RK+Rr=sum of contact forces (R)
400N+sum of R+(-700N)=0
700N-400N=sum of R
300N
The result of vectors added for two or more forces
Resultant force
This scale measures how acidic or basic a liquid is, from 0 to 14.
pH scale
Static=friction when two objects are not in motion
Limiting=the maximum value of static friction just before the two contacting surfaces
Dynamic=friction acting between two surfaces that are moving relative to each other
What are the equations for friction (static and dynamic)?
F=Us*R OR F=Ud*R
Where
F=Friction force
U=coefficient of friction
s=static
d=dynamic
R=normal contact force
Daisy walks across a force platform, and the forces exerted by her foot during a step are recorded. The peak vertical reaction force is 1200 N (this force acts upward on Daisy). At the same instant, the braking frictional force is 200 N (this force acts backward on Daisy).
c2=a2+b2
=(200N)2+(1200N)2
C=sqrt((200N)2+(1200N)2)
c=sqrt((1480000)2)
c=1217N
-----
theta=arctan(opp/hyp) = arctan(1200N/200N)
theta=80.5 degrees
a mechanical representation via a drawing
Free body diagram
This animal is known for having the fastest and most violent punch in the animal kingdom.
Mantis shrimp