Physics Review: Newton's Laws, Momentum, Impulse, and Energy

A comprehensive vocabulary review of 45 fundamental concepts, formulas, and principles from Newton's laws of motion, momentum, impulse, work, and energy.

Concept of Inertia (Origin)

The property of matter to resist changes in its state of motion, first introduced by Galileo Galilei and formalized by Isaac Newton into his first law of motion (credited as 'Both' in the lecture quiz).

Motion Under Vanishing Solar Gravity

The path Earth would follow if the gravitational pull between the Sun and Earth suddenly vanished: it would move in a straight-line path at constant velocity due to inertia.

Newton's First Law (Automobile Application)

The law of motion primarily linked to the necessity and function of seat belts and air bags in a car, protecting passengers who tend to maintain their state of forward motion during a collision.

Mechanical Equilibrium

The state of any object where the net external force acting on it is equal to zero ($\boldsymbol{\tau} = 0$, $\boldsymbol{F}_{\text{net}} = 0$).

Coin Drop in a Smoothly Riding Bus

An inertial scenario where a coin dropped from above your head in the aisle of a smoothly moving bus lands directly at your feet because it continues moving forward with the bus's horizontal velocity.

Inertial Reaction of a Ball in a Jerked Cart

The phenomenon where a resting ball in the middle of a cart is struck by the back of the cart when the cart is quickly jerked forward, because the ball remains at rest due to inertia.

Net Force on an Opposed $10\,kg$ Block

The combined force on a $10\,kg$ block simultaneously pushed eastward with $20\,N$ and westward with $15\,N$, which equals $5\,N\text{ east}$ ($20\,N - 15\,N = 5\,N$).

Acceleration of an Opposed $10\,kg$ Block

The acceleration resulting from a net force of $5\,N\text{ east}$ applied to a $10\,kg$ block, calculated as $a = \frac{F_{\text{net}}}{m} = \frac{5\,N}{10\,kg} = 0.5\,m/s^2\text{ east}$.

Newton's Second Law of Motion

The physical law establishing the relationship between net force, mass, and acceleration ($F = ma$), stating that acceleration is directly proportional to net force and inversely proportional to mass.

Impact Force of a Boxer's Punch

The force with which a punch lands, which depends fundamentally on the mass of what is being hit because an object can only exert as much force as the opposing object can return.

Earth's Motion from a Vertical Jump

The consequence predicted by Newton's third law when a person jumps vertically upward: the person exerts an equal and opposite downward force on Earth, causing Earth to move downward.

Rocket Propulsion Force

The propelling force that drives a rocket forward, provided directly by the reaction force of its expelled exhaust gases pushing backward against the rocket.

Simultaneity Criterion (Newton's Third Law)

The requirement that third-law action-reaction forces must occur simultaneously; everyday cause-and-effect sequences (such as being late and subsequently reprimanded) do not qualify as third-law interactions.

Resultant Range of a $50\,N$ and $30\,N$ Vector Pair

The possible magnitude range for combining two force vectors ($50\,N$ and $30\,N$), which must fall between $20\,N$ ($50\,N - 30\,N$) and $80\,N$ ($50\,N + 30\,N$); therefore, values such as $0\,N$, $85\,N$, and $90\,N$ are impossible.

Vertical Component of a $50\,N$ Vector

The perpendicular vertical component of a $50\,N$ vector having a horizontal component of $40\,N$, which equals $30\,N$ via the Pythagorean relationship ($\sqrt{(50\,N)^2 - (40\,N)^2} = 30\,N$).

Horizontal Component of a $100\,N$ Vector

The horizontal component of a $100\,N$ vector having a vertical component of $80\,N$, which equals $60\,N$ via the Pythagorean relationship ($\sqrt{(100\,N)^2 - (80\,N)^2} = 60\,N$).

Parallel Vector Resultants

The spatial relationship required for a $10\,N$ vector and a $5\,N$ vector to produce resultants of exactly $5\,N$ or $15\,N$: the two vectors must be parallel to each other.

Principles Employed for Moon Travel

The fundamental framework of physics utilized to plan missions, calculate orbital trajectories, and send humans to the Moon: Newton's laws of motion.

Momentum Under Doubled Mass and Speed

The change in an object's linear momentum ($p = mv$) when both mass and speed are doubled: momentum is quadrupled ($(2m)(2v) = 4mv$).

Momentum Under Halved Mass and Doubled Speed

The change in an object's linear momentum ($p = mv$) when its mass is reduced to half and its speed is doubled: momentum remains unchanged ($(0.5m)(2v) = 1mv$).

Impulse-Momentum Correction

The correction to the incorrect claim that 'impulse equals momentum': impulse equals the change in momentum ($J = \Delta p$), making 'change' the missing word.

Momentum Comparison (Car vs. Truck)

The comparison of momentum between a car and a heavy truck moving at the same speed down a hill: the truck has more momentum than the car because of its greater mass.

Momentum Comparison ($1\,kg$ vs. $10\,kg$ Ball)

The relative momentum of a $10\,kg$ ball compared to a $1\,kg$ ball traveling at twice its speed: the $10\,kg$ ball has $5\text{ times}$ as much momentum ($p_{10} = 10v$, $p_1 = 2v$, and $\frac{10v}{2v} = 5$).

Impulse Under Doubled Force and Duration

The effect on impulse ($J = Ft$) when both the applied force and the contact time are doubled: the impulse is quadrupled ($(2F)(2t) = 4Ft$).

Impulse Under Halved Force and Doubled Duration

The effect on impulse ($J = Ft$) when the applied force is halved and the contact time is doubled: the impulse remains unchanged ($(0.5F)(2t) = Ft$).

Kinetic Consequence of Doubling Speed

The dynamic quantity that doubles when a racing car's speed doubles: only its momentum doubles ($p \propto v$), whereas its kinetic energy quadruples ($KE \propto v^2$).

Theoretical Derivation of Impulse-Momentum

The fundamental law of mechanics from which the impulse-momentum theorem ($Ft = \Delta mv$) is directly derived: Newton's second law ($F = m\frac{\Delta v}{t}$).

Cannon Recoil Momentum

The momentum acquired by a recoiling cannon upon firing a cannonball: it is ideally equal in magnitude and opposite in direction to the momentum given to the cannonball.

Baseball Catch Deceleration Technique

The barehand catching strategy of pulling the hand backward to stop the ball slowly, which increases the impact duration ($t$) and minimizes the impact force ($F$).

Landing Impact Force Determinants

The set of physical variables determining the impact force experienced upon landing from a jump: jumping height, the softness or hardness of the ground, and how much you bend your knees ('all of the above').

Rate of Momentum Change (Brick Wall Collision)

The temporal rate at which a car's momentum is dissipated when impacting a rigid brick wall versus a soft haystack: the brick wall stops momentum quickly, generating severe impact forces.

Recoil Speed of a Roller-Blading Thrower

The backward speed of a skater who tosses a ball with a mass equal to one-tenth the skater's mass: the skater's recoil speed is one-tenth as much as the ball's speed ($v_{\text{recoil}} = \frac{v_{\text{ball}}}{10}$).

Momentum of Expelled Blank Gases

The momentum carried by hot gases ejected from a pistol firing a blank: it is the same in magnitude (and opposite in direction) compared to the momentum of the recoiling pistol.

Air Bag Operational Equation

The mathematical formula that best illustrates why air bags reduce occupant injury by lengthening deceleration time: $Ft = \Delta mv$.

Work (Physical Definition)

The mechanical quantity defined as the product of force and distance ($W = Fd$), contrasting with impulse which is the product of force and time.

Work Required for Doubled Elevation

The energy expended when raising an automobile twice as high on a service rack: it requires twice the work ($W = F \times 2d = 2W$).

Work Required for Doubled Vehicle Mass

The energy expended when raising an automobile of twice the mass to the same height: it requires twice the work ($W = 2F \times d = 2W$) because gravitational weight force is doubled.

Potential Energy Independence from Momentum

The principle showing that an object having momentum is not required to have potential energy (False); a body moving along a chosen zero-elevation datum possesses momentum without gravitational potential energy.

Property Coexistent with Kinetic Energy

The dynamic quantity that an object possessing kinetic energy must inherently also have: momentum, because possessing kinetic energy requires non-zero mass and velocity.

Kinetic Energy Loss in Inelastic Sticking

The post-collision kinetic energy of a system after moving clay with $1\text{ unit}$ of kinetic energy collides with and adheres to a stationary heavy bowling ball: less than one unit, as kinetic energy converts to thermal energy and deformation.

Kinetic Energy of a Tripled-Speed Airplane

The kinetic energy of an identical model airplane moving at three times the speed of another: because $KE \propto v^2$, it possesses $3^2 = 9\text{ times}$ the kinetic energy, which is 'more than four times as much'.

Free-Fall Comparison of Unequal Masses

A heavy object and a light object dropped from identical heights: neither their total energies nor their momentums are equal ('none of the above'), because their unequal masses yield unequal values for $mgh$ and $mv$.

Momentum in Inelastic Fish Ingestion

The total momentum of a swimming big fish after swallowing a stationary small fish: by conservation of momentum for the system, the combined momentum after lunch is the same as before.

Speed of Coupled Identical Freight Cars

The post-collision speed of two identical coupled freight cars after a moving freight car hits a stationary freight car: exactly half of the initial speed of the first car ($mv = 2m(v') \rightarrow v' = \frac{v}{2}$).

Law of Conservation of Momentum

The fundamental principle stating that in the absence of an external net force, the total momentum of an isolated system remains unchanged across all collisions and interactions.