Linear Kinetics Flashcards
Force definition
Mechanical action or effect applied to a body that tends to produce acceleration
What is the unit of force? How do these units compare to pounds?
Newtons
1 lb = 4.448 N
What is the purpose of a free body diagram (FBD)
Simple diagram of an isolated object of interest designed to understand the externally applied forces on an object
What must be followed when making a FBD?
Newton’s laws
What is the first law of motion?
Law of inertia
What is the second law of motion?
Law of acceleration
What is the third law of motion?
Law of action reaction
What is the law of inertia?
An object in motion stays in motion unless acted upon by an outside force
Inertia
Resistance of a body to change its state of motion/keeping something in a constant state
What is uniform motion?
Constant momentum (m)(v)
What is the law of acceleration?
F=ma
when m is constant
An object’s change of motion is proportional to the force acted on it in the direction of the straight line where the force is impressed
What is acceleration referring to?
Of the object’s center of mass (COM)
What is the linear equation of motion (EOM)
F=ma
What is the inertial force known as in the EOM
ma
Statics
Branch of mechanics where a system undergoes no acceleration
(Velocity is constant)
Dynamics
Branch of mechanics where a system undergoes an acceleration
(Velocity is not constant)
True or false:
A static object means it always has no velocity
False
Static means constant velocity so it is still moving, just with no acceleration
Match static, dynamic, equilibrium, and not in equlibrium
Static- in equilibrium
Dynamic- not in equilibrium
True or false:
Static mechanics only cares about kinetics
False:
Cares about kinematics too since it can still have a velocity
What is the law of action reaction?
For every action there is an equal and opposite reaction
True or false:
Forces cancel out in Newtons 3rd law
False
One force acts on one object and the other on another object
What is the law of universal gravitation?
All objects attract each other with a gravitational force inversely proportional to the square distance between objects
What does the force of gravity depend on the proportionality of?
Masses of the two bodies being attracted to each other
Mass (m)
How much matter is in an object
Scalar
Weight (W)
Force due to gravitational acceleration
Vector
True or false
Body weight (N) = Body mass (kg)
False
These are not interchangeable
Center of mass (COM)
The point in which all the particles of the body are evenly distributed
Always exists
Center of Gravity
Point in which weight due to gravity acts on a body
Exists when gravity exists
Ground reaction force
Distributing force
Term that includes the normal and tangential (friction) force
Center of pressure
Singular point of application of the ground reaction force (GRF)
Which type of forces are we more concerned with?
External forces
True or false:
Muscle forces would be considered internal forces
True
What three things at a joint can alter the COM motion of a body segment?
Muscles
Ligament
Bone on bone forces
Kinematics
Area of study that examines the spatial and temporal components of motion
Position, velocity, acceleration, etc…
Kinetics
Study of the causes of motion
Forces, torque, impulse, momentum, work, power, energy
True or false:
Kinetics is the study of both motion and the causes for motion
False
Only the causes for motion
Is force a vector or scalar?
Vector- includes magnitude and direction
Is gravity an internal or external force?
External (affects the COM)
Does the force of gravity change depending on where you are on Earth?
Yes- elevation affects gravity
The property of an object to resist motion
Inertia
The law of inertia describes _______ conditions with the sum of the external forces equal to zero
Static
When does linear momentum only need to stay constant?
When the external forces sum to zero
In order to use EOM, what must remain constant with time?
Mass
External forces causes changes in the _____ while internal forces may alter the object’s _____
COM
Shape
Muscles would be an example of what type of force?
Internal
How would you find the direction of acceleration from vectors?
Split into x and y components and determine the greater magnitude and direction
