Biomechanics Exam 2
State Newton's 1st law of motion. - Answer-Law of inertia
objects at rest will remain at rest and objects in motion will remain in motion in a straight line unless
acted on by an external force
State Newton's 2nd law of motion. - Answer-fundamental law of dynamics or law of acceleration
-A=F/M or F=MA
-acceleration = change in motion
-small masses accelerate easier
State Newton's 3rd law of motion. - Answer-Law of reciprocal actions, or law of action-reaction
-To every action there is always opposed an equal reaction, or, the mutual actions of two bodies upon
each other are always equal and directed to contrary parts.
-forces exist in pairs
State Newton's law of Universal gravitation - Answer-law of gravitation, or law of attraction
, states that a particle attracts every other particle in the universe using a force that is directly
proportional to the product of their masses and inversely proportional to the square of the distance
between their centers
When we exert a force on the earth, its mass is too large to allow our segment (leg) to move away from
the body. Therefore, what must the body be doing in relation to the
segment in order for us to move? - Answer-The leg pushes onto the earth, but the earth is more
massive so earth "pushes back" and the body moves away from the leg. Since the earth is in the way and
we extend our leg it forces us to move a away from the earth
Friction depends on what 2 factors? (do not just give the pieces of the equation above; define the pieces
of the equation for this answer) - Answer--Normal force - the force pushing two objects together.
-Coefficient of friction - the two objects and the nature of their surfaces
-----the ratio of the force needed to move one surface horizontally and the pressure between the two
forces
What does it mean if the coefficient of friction for 2 surfaces is equal to 0.0? What if it is equal to 1.0? -
Answer--A coefficient of 0.0 indicates a totally frictionless interaction.
-A coefficient of 1.0 indicates what is, arguably, the highest degree of friction. Anything higher than 1.0
is more of an adhesion interaction rather than friction.
The coefficient of friction for a synovial joint is 0.001. Why is this important? - Answer-This coefficient is
one of the smallest, which indicates that it is not a completely frictionless interaction, but it has minimal
friction. Synovial joints are fluid filled sockets that limit friction for the health of the
bones/tendons/muscles/cartilage involved in movement.
How can friction be both resistive and motive during running? - Answer-Friction is motive in that it
provides the force for an acceleration and resistive in that it keeps the foot from slipping while changing
direction
State Newton's 1st law of motion. - Answer-Law of inertia
objects at rest will remain at rest and objects in motion will remain in motion in a straight line unless
acted on by an external force
State Newton's 2nd law of motion. - Answer-fundamental law of dynamics or law of acceleration
-A=F/M or F=MA
-acceleration = change in motion
-small masses accelerate easier
State Newton's 3rd law of motion. - Answer-Law of reciprocal actions, or law of action-reaction
-To every action there is always opposed an equal reaction, or, the mutual actions of two bodies upon
each other are always equal and directed to contrary parts.
-forces exist in pairs
State Newton's law of Universal gravitation - Answer-law of gravitation, or law of attraction
, states that a particle attracts every other particle in the universe using a force that is directly
proportional to the product of their masses and inversely proportional to the square of the distance
between their centers
When we exert a force on the earth, its mass is too large to allow our segment (leg) to move away from
the body. Therefore, what must the body be doing in relation to the
segment in order for us to move? - Answer-The leg pushes onto the earth, but the earth is more
massive so earth "pushes back" and the body moves away from the leg. Since the earth is in the way and
we extend our leg it forces us to move a away from the earth
Friction depends on what 2 factors? (do not just give the pieces of the equation above; define the pieces
of the equation for this answer) - Answer--Normal force - the force pushing two objects together.
-Coefficient of friction - the two objects and the nature of their surfaces
-----the ratio of the force needed to move one surface horizontally and the pressure between the two
forces
What does it mean if the coefficient of friction for 2 surfaces is equal to 0.0? What if it is equal to 1.0? -
Answer--A coefficient of 0.0 indicates a totally frictionless interaction.
-A coefficient of 1.0 indicates what is, arguably, the highest degree of friction. Anything higher than 1.0
is more of an adhesion interaction rather than friction.
The coefficient of friction for a synovial joint is 0.001. Why is this important? - Answer-This coefficient is
one of the smallest, which indicates that it is not a completely frictionless interaction, but it has minimal
friction. Synovial joints are fluid filled sockets that limit friction for the health of the
bones/tendons/muscles/cartilage involved in movement.
How can friction be both resistive and motive during running? - Answer-Friction is motive in that it
provides the force for an acceleration and resistive in that it keeps the foot from slipping while changing
direction
