Week 1.2

Question 1

What are the three basic dimensions in mechanics?

Answer 1

Length, Time, Mass

These dimensions are empirical concepts based on experience and experiment.

Question 2

What is the basic SI unit for length?

Answer 2

meter (m)

1 m is approximately 3.28 ft or 39 in.

Question 3

What is the basic SI unit for time?

Answer 3

second (s)

Time orders the sequences in the universe.

Question 4

What is the basic SI unit of mass?

Answer 4

kilogram (kg)

Mass is the quantity of matter that makes up an object.

Question 5

What does mass determine in relation to motion?

Answer 5

The effort needed to change the current state of motion of an object.

Question 6

Is mass the same as weight?

Answer 6

No

Mass is the quantity of matter, while weight is the force of gravity acting on that mass.

Question 7

What is inertia?

Answer 7

The resistance of an object to changes in its state of motion.

Question 8

What is the Center of Mass (COM)?

Answer 8

A point in space that moves as if the whole body was concentrated at that point.

Question 9

How does the position of the COM depend on the object?

Answer 9

It depends on the distribution of the mass of the object.

Question 10

Where is the COM located in the human body when standing in anatomical position?

Answer 10

55-57% of body height, approximately at the level of the umbilicus.

Question 11

What is the Center of Gravity (COG)?

Answer 11

The point at which the body can be balanced by a gravitational field.

Question 12

What is a scalar quantity?

Answer 12

A quantity completely defined by its magnitude.

Question 13

What are some examples of scalar quantities?

Answer 13

• Time
• Distance
• Energy
• Volume
• Mass
• Work
• Power
• Speed

Question 14

What is a vector quantity?

Answer 14

A quantity that possesses magnitude and direction.

Question 15

How do vector quantities add?

Answer 15

According to the Parallelogram Law.

Question 16

What is the SI unit of force?

Answer 16

Newton (N)

1 N = 1 kg.m/s²

Question 17

What does force cause in terms of motion?

Answer 17

Changes in the motion of an object, or accelerations.

Question 18

What is the line of action in relation to force vectors?

Answer 18

An imaginary line that extends along the shaft of the force vector.

Question 19

What are external forces?

Answer 19

Forces that act on a system of interest due to interaction with the surrounding environment.

Question 20

What are contact external forces?

Answer 20

Forces resulting from two or more objects in contact with one another.

Question 21

What is the Universal Law of Gravitation?

Answer 21

Describes the force of attraction between two bodies and defines the concept of weight.

Question 22

What is the formula for gravitational attraction?

Answer 22

F = G(m1 * m2) / r²

Question 23

What does weight (W) equal in terms of mass (m) and gravitational acceleration (g)?

Answer 23

W = mg

Question 24

What is the acceleration due to gravity (g)?

Answer 24

-9.81 m/s²

The negative sign indicates direction toward the center of the earth.

Question 25

What are internal forces?

Answer 25

Forces that act within a body or segment being assessed.

Question 26

What happens when external forces exceed internal forces?

Answer 26

The structure fails.

Question 27

What are internal forces?

Answer 27

Forces that act within a body/segment being assessed ## Footnote Internal forces help maintain the structure and prevent deformation.

Question 28

What happens if external forces applied to a segment exceed internal forces?

Answer 28

The structure fails ## Footnote This indicates the importance of internal forces in maintaining the integrity of the body.

Question 29

In the context of biomechanics, what is a system of interest?

Answer 29

The whole body or a defined segment of the body ## Footnote It is the focus of the analysis regarding forces and motion.

Question 30

What is the significance of the center of mass (COM) in motion?

Answer 30

To change the motion of the whole body COM, external force(s) must act on the body. ## Footnote The COM is crucial for understanding overall body motion.

Question 31

What does Newton's First Law of Motion state?

Answer 31

An object at rest or moving at a constant speed will remain so until acted upon by a non-zero resultant external force. ## Footnote This law explains inertia and the conditions for changing motion.

Question 32

What is the mathematical expression for Newton's First Law of Motion?

Answer 32

v = linear velocity of the object; Σ F = the resultant external force acting on the object ## Footnote Σ represents the sum of all forces.

Question 33

What does Newton's Second Law of Motion describe?

Answer 33

If a non-zero resultant external force acts on an object, the object will accelerate in the direction of that force. ## Footnote This law relates force, mass, and acceleration.

Question 34

How is linear acceleration expressed mathematically in Newton's Second Law?

Answer 34

Σ F = m * a ## Footnote This shows the relationship between force, mass, and acceleration.

Question 35

What does Newton's Third Law of Motion state?

Answer 35

To every action, there is always opposed an equal reaction. ## Footnote This law emphasizes the interaction between two bodies.

Question 36

Fill in the blank: If the resultant external force acting on an object is zero, the object will _______.

Answer 36

remain at rest or continue moving at a constant velocity ## Footnote This is a consequence of Newton's First Law.

Question 37

What type of mechanics studies the internal forces within a body?

Answer 37

Deformable body mechanics ## Footnote This field examines how materials deform under stress.

Question 38

What is required to change the motion of an object?

Answer 38

The presence of a non-zero net (resultant) external force ## Footnote This is a critical principle in dynamics.