Grade 11 Physics: Forces and Newton's Laws

Vocabulary flashcards covering the fundamentals of forces, normal force, static and kinetic friction, inclined plane components, free-body diagrams, equilibrium, and Newton's three laws of motion.

Force

A push or pull that arises from the interaction between two objects.

Normal Force ($F_N$)

The perpendicular force exerted by a surface on an object in contact with it.

Frictional Force ($F_f$)

The force that opposes the motion of an object and acts parallel to the surface with which the object is in contact.

Static Friction

The frictional force experienced between an object and a surface when the object is stationary only, which is directly proportional to the normal force.

Maximum Static Frictional Force ($F_{fs}^{\max}$)

The maximum frictional force that must be overcome for an object to start moving, calculated as $F_{fs}^{\max} = \mu_s F_N$.

Kinetic Friction

The frictional force experienced between an object and a surface when the object is moving over and in contact with the surface, calculated as $F_{fk} = \mu_k F_N$. It is independent of the speed of the moving object.

Coefficient of Friction

The ratio between the friction experienced and the normal force of an object, represented as a dimensionless number with no unit.

Perpendicular Component of Weight ($F_{g\perp}$)

The component of an object's weight holding it onto an inclined plane, given by $F_{g\perp} = m g \cos(\theta)$.

Parallel Component of Weight ($F_{g\parallel}$)

The component of an object's weight acting down along the slope of an inclined plane, given by $F_{g\parallel} = m g \sin(\theta)$.

Free-Body Diagram

A diagram that represents the mass of an object as a dot, with all acting forces drawn as vectors starting from the centre of mass and pointing radially outward.

Equilibrium

The state of an object when all the forces acting on it provide a resultant (net) force of zero ($F_{\text{net}} = 0\,\text{N}$), resulting in the object remaining stationary or moving at constant velocity.

Equilibrant

The force equal in magnitude and opposite in direction to the resultant of all other forces acting on an object.

Triangle Law of Forces

A principle stating that when three forces acting on an object are in equilibrium, they can be represented in magnitude and direction by the sides of a closed triangle drawn head-to-tail.

Newton’s First Law of Motion

An object continues in a state of rest or uniform (moving with constant) velocity unless it is acted upon by a net or resultant force.

Inertia

The property of an object that causes it to resist a change in its state of rest or uniform motion.

Newton’s Second Law of Motion

When a net force ($F_{\text{net}}$) is applied to an object of mass ($m$), it accelerates in the direction of the net force; the acceleration ($a$) is directly proportional to the net force and inversely proportional to the mass ($F_{\text{net}} = m a$).

Newton’s Third Law of Motion

When object A exerts a force on object B, object B simultaneously exerts an oppositely directed force of equal magnitude on object A.