Module 5 & 6: Biomechanics of Human Movement Flashcards
Name the 3 Newton’s Laws.
Law of Inertia
Law of Acceleration
Law of Action and Reaction
Describe the Law of inertia.
Objects won’t move unless something makes them move, and they won’t stop unless something stops them
Things stay put unless pushed or pulled.
Describe the Law of acceleration.
The more force you apply to an object, the more it will accelerate, depending on how heavy it is.
The harder you push, the faster it goes.
Describe the Law of action and reaction.
If you push on something, it pushes back with the same force.
For every action, there’s an equal and opposite reaction.
What is force? Give 2 examples.
A push or pull exerted on an object that can cause it to move, stop, or change direction. It is measured in newtons (N) and can affect the motion of objects in various ways.
Pushing a Swing: When you push a swing, the force causes it to move. The harder you push, the faster and farther the swing moves.
Gravity: The force of gravity pulls objects toward the Earth.
What are vectors?
A mathematical quantity that has both magnitude (size / length) and direction.
The length of the arrow shows the magnitude (how big the quantity is).
The direction of the arrow shows the direction of the quantity (which way it’s pointing).
How is force calculated and what is its unit?
Force = Mass × Acceleration:
F = m × a (in Newtons, N)
1 Newton (N) = 1 kilogram meter per second squared (kg·m/s²), which means it is the force needed to accelerate 1 kg of mass by 1 meter per second squared.
What is the difference between one-dimensional and two-dimensional force systems?
One-dimensional force system: forces acting on the same plane and line of action. (A book sitting on a table, gravity is pulls it downward, the table pushes up with equal force.)
Two-dimensional force system: forces acting on the same plane BUT NOT in the same line of action. (A book on a table is being pushed from the side (horizontal force) while gravity pulls it downward (vertical force).
Define coplanar, parallel, orthogonal and concurrent forces.
Coplanar: Forces act in the same plane but in different directions.
(Pushing the book to the right while someone else pushes it at a slight angle on the same plane.)
Parallel: Forces move in the same or opposite directions and are parallel to each other.
(Two people pushing a cart from the same side or opposite sides.)
Orthogonal: Forces are at right angles (90°) to each other.
(Pushing a box sideways while gravity is pulling it down.)
Concurrent: Forces start from the same point, or their paths meet at one point.
(Multiple ropes pulling a hot air balloon from different angles.)
What is a resultant force and how is it calculated?
The overall effect of all forces acting on an object.
The single force obtained by analyzing the force systems.
Collinear (acting along the same line): If acting in the same direction, add the magnitudes; if acting in opposite directions, subtract the smaller force from the larger one.
Coplanar (acting in the same plane but not necessarily along the same line of action): Connect the ends of the vectors to form a parallelogram.
Parallel (parallel to each other in the same or opposite direction): If acting in the same direction, add the magnitudes; if acting in opposite directions, subtract the smaller force from the larger one.
Orthogonal (at right angles): Connect the ends of the vectors to form a parallelogram.
Concurrent (start from the same point): Sum the forces if acting in the same direction.
Define gravity.
The force of attraction that pulls objects toward the center of the Earth.
~10 m/s²
Define centripetal force.
The force that keeps an object moving in a circular path.
Acts perpendicularly (orthogonally) to the object’s velocity and is directed toward the center of the circular path.
To maintain circular motion, a continuous force must be applied to change its direction, preventing it from moving in a straight line.
Carnival ride: the centripetal force is the ride’s wall. It exerts an inward force toward the center of the circle, allowing the people to move in a circular path instead of flying outward as the ride spins. what keeps people pressed against the outer wall of the ride as it spins.
Define friction.
A force that occurs between two surfaces in contact, resisting movement. It tries to stop or slow down moving objects. It always acts in the opposite direction to the movement. If you push an object to the right, it pulls to the left.
Static Friction: occurs when two surfaces are not moving relative to each other. It prevents motion until enough force is applied.
Dynamic (Kinetic) Friction: occurs when surfaces are already moving against each other. It resists further movement.
Define elastic force.
The force exerted by an elastic material when it is deformed (stretched or compressed) by an external force.
Elastic Materials: are objects that can change shape when a force is applied but return to their original shape when the force is removed.
Direction of Force: The elastic force typically acts in the opposite direction to the deformation, meaning the material tries to return to its original shape.
Deformation: How much a material deforms (changes shape) depends on the load (force) applied and the material’s stiffness. Stiff materials resist deformation more than flexible ones.
Human Body Example: Different body parts have different stiffness. Muscles can stretch more easily than ligaments. When forces act on the body (like during movement), these parts respond differently based on their stiffness.
Load Direction: Body parts endure loads in various directions, and they resist these loads in different ways depending on their structure.
Define ground reaction force.
The force the ground exerts back when you apply a force to it, following Newton’s 3rd Law (every action has an equal and opposite reaction).
Standing: Your body pushes down on the ground (gravity, your weight), and the ground pushes up with an equal force, keeping you balanced and upright.
Jumping: You push down on the ground, and it pushes you back up, helping you jump.
Running: As your foot hits the ground, it pushes back both upwards (to support your weight) and forwards (to help you move forward).
Wall Push-ups: You push against the wall, and the wall pushes back with equal force, allowing you to push yourself away from it. This is like ground reaction force, but from a wall.
What factors will influence the amount of deformity suffered by an object?
Type of Material:
Elastic Materials: can be stretched or compressed and will return to their original shape once the force is removed.
Non-Elastic Materials: may not return to their original shape after being deformed
Applied Load: the size and direction of the force applied to the object affects how much it deforms. A greater load typically results in more deformation.
Material Stiffness: refers to how resistant a material is to deformation. Stiffer materials deform less under the same load.
Direction of Load: different body parts experience loads from various directions, and their ability to resist deformation varies. Muscles and ligaments respond differently when stressed.
Duration of Load: the length of time a force is applied can impact deformation. Continuous loading may lead to more significant deformation, especially in viscoelastic materials.
What is moment or torque?
The turning force that results from applying a force at a distance from a pivot point or axis of rotation.
A tire ratchet, as an example.
How is moment calculated?
Moment = Force x Distance
The further from the axis, the easier to cause moment/torque.
What is the definition of a lever?
A rigid bar that rotates around a fixed point aka fulcrum
