Lesson 3

Vocabulary flashcards covering net force, Newton's laws, seatbelt design criteria/constraints, mass, friction, and related concepts from the notes.

Net Force

The vector sum of all forces acting on an object; if forces act in the same direction, they are added; if opposite directions, they are subtracted; it determines the object's acceleration.

Balanced Forces

Forces whose net force on an object is zero; the object either remains at rest or continues moving at a constant velocity.

Unbalanced Forces

Forces whose net force on an object is not zero; they cause acceleration or a change in motion.

Newton's First Law

An object at rest stays at rest, and an object in motion stays in motion with a constant velocity unless acted on by an unbalanced force.

Object at Rest

An object that is not moving; if forces are balanced, it will remain at rest.

Object in Motion

An object that is moving with constant velocity when forces are balanced.

Acceleration

The rate of change of an object's velocity; according to Newton's second law, acceleration equals net force divided by mass (a = F/m).

Mass

A measure of the amount of matter in an object; mass affects how much an object accelerates for a given net force (larger mass = smaller acceleration for the same net force).

Force

A push or pull on an object; a vector quantity with both magnitude and direction.

Friction

A force that opposes motion between two surfaces in contact; can slow motion (negative acceleration) but is useful for stopping or gripping.

Newton's Second Law

Acceleration of an object equals the net force acting on it divided by its mass (a = F/m); also expressed as F = m a.

Three-Point Seatbelt

A seatbelt design with two straps joined at three points to restrain both upper and lower body; top strap over the shoulder, bottom strap near the hips; designed to be secure with one hand.

Criteria

Design requirements that a solution must meet; what the solution should achieve.

Constraints

Design limits or restrictions on a solution, such as cost and ease of manufacture.

Inertia

The resistance of any physical object to a change in its state of motion or rest.