Physics Kinematics and Forces Quiz

Units

• Physics deals with quantities measured with units, such as meters for length and seconds for time.
• Units are carefully defined amounts of a quantity.
• Physics uses the International System of Units (SI), based on the metric system and using base units like meters, seconds, and kilograms.
• Common derived units can be expressed as combinations of base SI units, like speed being meters per second (m/s).

Kinematics

• Kinematics studies the motion of bodies.
• Distance represents the total length of the path traveled.
• Displacement is the change in position with direction, a vector quantity.
• Average velocity is the displacement divided by the elapsed time.
• Average speed is the total distance traveled divided by the time.
• Acceleration is the change in velocity over time.

Forces

• Force is a measurable influence that causes a change in the motion of an object.
• Newton's first law states that an object at rest or moving at constant velocity remains that way unless acted on by an external force.
• Newton's second law describes the relation between force, mass, and acceleration: 𝐹 = 𝑚𝛼.
• Newton's third law states that for every action, there is an equal and opposite reaction force.
• Weight is the force due to gravity acting on an object, calculated as W = mg, where g is the acceleration due to gravity (9.81 m/s²).

Normal, Friction, and Tension Forces

• Normal force is the force exerted by a surface perpendicular to the object in contact.
• Friction opposes motion between two surfaces in contact.
• Tension force occurs in ropes and strings when they are pulled taut.

Torque

• Torque represents the tendency of a force to rotate an object around an axis, fulcrum, or pivot point.
• Torque can be thought of as a twist.

Equilibrium

• A system is in equilibrium when the net force and net torque on it are zero.
• Static equilibrium occurs when the system is in equilibrium and stationary.
• Stable equilibrium implies the system returns to its equilibrium position after a small displacement.
• Unstable equilibrium means the system does not return to its equilibrium position after a small displacement.

Standing Stability

• Stability during standing is essential for maintaining balance.
• For overall stability, the center of mass must be over the area spanned by the feet.
• If the center of mass is outside the support base, the system is unstable and may topple over.
• The line of gravity passing through the center of the support base signifies stable equilibrium.
• We are most stable when the line of gravity falls closer to the center of the support base.

Medical Terminology

• The term "pericarditis" refers to inflammation surrounding the heart.
• It is constructed from the prefix "peri-" meaning "surrounding," the root "cardi" meaning "heart," and the suffix "-itis" meaning "inflammation."
• The term "phonocardiography" refers to the graphic recording of heart sounds.
• It is constructed from the prefix "phono" meaning "sound," the root "cardi" meaning "heart," and the suffix "graph" meaning "write."

Prefixes and Units

• Prefixes are used to represent quantities in powers of 10.
• Common prefixes include: pico-, nano-, micro-, milli-, centi-, kilo-, mega-, giga-, tera-.
• Prefixes are used to express very large or very small numbers more conveniently.
• For example, a nanosecond is one billionth of a second (1 x 10^-9 seconds).

Changing Units

• Changing units involves multiplying the original measurement by a conversion factor.
• A conversion factor is a ratio of units equal to unity.
• For example, to convert minutes to seconds, multiply by (60 seconds/ 1 minute).

Accuracy, Uncertainty, and Significant Figures

• Accuracy refers to how close a measurement is to the true value.
• Precision refers to the reproducibility of a measurement.
• Uncertainty is a numeric measure of confidence in a measurement, with lower uncertainty indicating greater confidence.
• Leading zeros are never significant.
• Imbedded zeros are always significant.
• Trailing zeros are significant only if the decimal point is specified.

Forces and Newton's Laws

• Force is a measurable influence that causes a change in an object's motion.
• Newton's first law states that an object at rest or in motion will remain in that state unless acted upon by an external force.
• Newton's second law states that the acceleration of an object is directly proportional to the force applied and inversely proportional to its mass (F = ma).
• The SI unit of force is the Newton (N).
• Weight is a force due to gravity and is expressed in Newtons.

Equilibrium and Stability

• A system is in equilibrium when the net force and net torque on the system are zero.
• A system in static equilibrium is in equilibrium and stationary.
• A system in stable equilibrium will return to equilibrium after a small displacement.
• A system in unstable equilibrium will not return to its equilibrium state after a small displacement.
• Stability during standing requires the center of mass to be over the area spanned by the feet.
• When the line of gravity is near the center of the support base, an individual is most stable.
• When leaning, the line of gravity may pass through the periphery of the base or even outside it, resulting in less stability.

Torque

• Torque is the tendency of a force to rotate an object about an axis, fulcrum, or pivot.
• It can be thought of as a "twist."