Newton's Laws of Motion and Balanced Forces

Comprehensive vocabulary flashcards covering Newton's First, Second, and Third Laws of Motion, balanced and unbalanced forces, vehicle safety systems, and rocket flight.

Newton's First Law

A law stating that an object will remain at rest or continue traveling at a steady speed in a straight line unless acted upon by an unbalanced force.

Newton's Second Law

A law stating that an object will accelerate when acted upon by an unbalanced force, described mathematically by the formula $F = ma$ (or $F_{un} = ma$).

Newton's Third Law

A law stating that if object A exerts a force on object B, then object B exerts an equal but opposite force on object A.

Balanced Forces

Forces acting on an object that are equal in size and opposite in direction, resulting in no overall change in velocity (steady speed or stationary).

Unbalanced Force ($F_{un}$)

A resultant non-zero force that causes a mass to accelerate.

Thrust

The forward engine force that accelerates an aircraft or vehicle forward.

Drag

Air resistance acting against the motion of an aircraft or moving vehicle that increases with speed until forces become balanced.

Lift

An upward aerodynamic force developed by the wings of an aircraft that depends on flight speed and balances the downward weight.

Balanced Forces on an Aircraft

A state in steady flight where the forward engine thrust equals air resistance (drag) and upward lift equals the aircraft's weight.

Upthrust

The upward force exerted by a fluid (such as water) on a floating object that balances its weight.

Addition of Forces

The method of determining the combined effect of two or more forces acting in the same direction by adding their magnitudes together ($F + F = 2F$).

Subtraction of Forces

The method of determining the combined effect of forces acting in opposite directions by taking one force away from another ($F - F = 0F$).

Action-Reaction Pairs

Equal and opposite force interactions occurring simultaneously between two interacting objects (e.g., bullet accelerating forward while recoil acts on the gun).

Seatbelt Function (Newton's First and Second Laws)

A safety restraint that applies a backward unbalanced force to bring an occupant to a stop safely at the same rate as the car, preventing them from continuing forward into the windscreen.

Airbags and Crumple Zones

Automotive safety features designed to protect passengers during a crash because deceleration forces can still be very large despite seatbelts.

Rocket Propulsion Forces

The downward push of the rocket against exhaust gases acts as the action force, while the upward push of the exhaust gases on the rocket acts as the reaction force.

Newton's First Law in Space

Because space has no atmosphere and no air resistance, a spacecraft with engines switched off maintains its initial speed or spin until thrusters fire in the opposite direction.

Free Fall

The downward acceleration of an object solely under the influence of gravity, causing all objects to accelerate downwards at $9.8\,\text{ms}^{-2}$.