newtonian mechanics flashcards

What two major scientific works were published by Sir Isaac Newton in 1687 and 1704, respectively?

1. Mathematical Principles of Natural Philosophy

2. Opticks(1704)

Which German mathematician was involved in a fierce dispute with Issac’s Newton over who first invented calculus?

Gottfried Wilhelm Leibniz

According to Aristotle’s incorrect theory of motion, how did an object’s weight affect its falling speed?

Aristotle believed heavier objects were more strongly attracted to Earth and therefore fell faster than lighter ones

How did Aristotle contrast the natural motion of celestial sphere objects with terrestrial sphere objects?

Celestial objects moved naturally in circular motion without external forces, while terrestrial objects moved in straight lines unless acted upon.

What condition is strictly required to change either the speed or direction of of an object’s motion?

A non-zero net force acting on the object.

What defines an inertial reference frame in Newtonian mechanics?

An inertial reference frame is one in which Newton’s First Law is true.

Why are accelerating reference frames classified as non-inertial frames?

Because objects inside accelerating frames experience apparent accelerations without an external net force acting on them, violating Newton’s First Law.

Why is force mathematically classified as a vector quantity?

Because force has both magnitude and a direction, requiring vector algebra for summation.

In physics, what does an object’s mass quantify?

Mass quantifies an object’s resistance to changing its velocity, as well as the quantity of matter within it.

If the net force acting on a body is zero, what are the implications for its acceleration and state of motion?

The acceleration is zero and the forces acting on the body are equilibrium.

Why are internal forces omitted from a system’s overall Free-Body diagram when calculating system acceleration?

Internal forces in equal and opposite action-reaction pairs between objects inside the system, so they sum to zero and cannot accelerate the overall system.

According to Newton’s Third Law, if Object 1 exerts a force F on Object 2, what force does Object 2 exert on Object 1?

Object 2 exerts an equal and opposite force-F on Object 1.

Do the two forces comprising a Newton’s Third Law action-reaction pair act on the same object or on different objects?

They always act on different objects. Therefore, they never cancel each other out on a single object’s free-body diagram.

Consider two blocks touching on a frictionless surface: does the contact force between the blocks depend on which block is directly pushed?

Yes, although total acceleration is the same, the contact force transferred across the interface differs depending on which block receives the applied force F.

How are the scalar components F2,x and F2,ty expressed for force F2 at angle theta= 52?

• F2,x= F2cos52

• F2,y= F2sin52

What are the four fundamental forces that govern all matter in the universe?

1. Strong force

2. Electromagnetic force

3. Weak force

4. Gravitational force

Rank the four fundamental forces of nature from strongest to weakest in relative strength

1. Strong force

2. Electromagnetic force

3. Weak force

4. Gravitational force

Which two of the four fundamental forces have an infinite range of action?

The electromagnetic force and gravity.

What is the key distinction between an object’s mass and its weight?

Mass- an intrinsic scalar property measuring inertia

Weight- the gravitational pull of exerted on that mass, measured in Newtons

A person stands on a scale inside an elevator: how does apparent weight compare to actual weight when the elevator accelerates upward at a.

Apparent weight is greater than actual weight because normal force must accelerate the person upward against gravity.

What is a passenger’s apparent weight if an elevator snaps its cable and goes into free fall (a=g downward)

Zero. Because both passenger and floor accelerates downward at g, contact force drops to zero (N=0)

An object on a flat surface is pulled upward at angle theta by force F:

How does the normal force N compare to the gravitational weight W?

The normal force is less than weight (N=W-Fsintheta) because the vertical component of the pulling force supports part of the load.

What is the definition of a normal force?

The perpendicular contact force exerted by a supporting surface on an object to prevent it from penetrating the surface.

what physical mechanism causes friction between two surfaces at a microscopic level?

Friction arises because surfaces are not completely smooth; microscopic high points, asperities, collide and interlock when sliding.

In what direction does the force of friction always act relative to motion?

Friction always acts in the direction opposing the direction of motion.

What is kinetic friction?

Kinetic friction is the resistive force experienced by surfaces that are actively sliding against one another.

What is static friction?

Static friction is the force that opposes the initiation of relative sliding motion between two contacting surfaces at rest.

What is the mathematical equation for kinetic friction fk?

fk= mulekN where mulek is the coefficient of kinetic friction and N is the magnitude of the normal force

What inequality describes the maximum static friction force fs?

fs<mulesN where mule s is the coefficient of static friction and N is the normal force.

How does doubling the weight of a sliding object affect the kinetic friction force?

Doubling the weight doubles the normal force (2N), which directly doubles the kinetic force(2fk)

How does the area of contact between two surfaces affect kinetic friction?

Kinetic friction is independent of the contact area between the sliding surfaces.

What defines weight in Newtonian mechanics?

The force of gravity acting on an object’s mass, calculated as weight equals mass times gravitational acceleration (W=mg), directed toward the center of the Earth.

Why do opposing surfaces experience friction when moving relative to each other?

Friction is caused by microscopic surface roughness, where irregular microscopic peaks and valleys on opposing surfaces interlock and resist relative sliding.

What is kinetic friction?

The resistive frictional force experienced between solid surfaces that are actively sliding against one another.

How do relative sliding speed and surface contact area affect kinetic friction?

Kinetic frictional force is independent of both the relative sliding speed of the surfaces and their area of contact.

What is the mathematical relationship between kinetic friction and normal force?

Kinetic friction is directly proportional to the normal force. Stacking an identical box doubled the normal force(2N), which doubles the line friction force(2fk).

How does the static coefficient of friction (mule s) typically compare to the kinetic coefficient of friction( mule k) for a given pair of materials?

The static coefficient is generally greater than the kinetic coefficient, meaning more force is required to break static friction and start motion than to maintain sliding motion.

How does the vertical component Fy affect the magnitude of the normal force Fn?

The downward component Fy increases the total normal force above the weight of the block: Fn = Fg + Fy

Why is a rope usually assumed to be massless in introductory physics problems?

Assuming a rope is massless ensures that tension remains uniform throughout its entire length. In a real rope, tension varies along the length due to the rope’s own weight.

What is Hooke’s Law for springs?

Hooke’s Law states that the restoring force exerted by a spring is directly proportional to its displacement from equilibrium: F = -kx(where k is the spring constant)

What does the spring constant k measure?

It measures the stiffness of a spring, representing the restoring force required per unit extension or compression.(N/m)

What condition must be met for an object to be in translational equilibrium?

The vector sum of all external forces acting on the object must be equal to zero: ΣF = 0

Does translational equilibrium imply that an object is stationary?

No. An object in translational equilibrium has zero acceleration, meaning it is either at rest or moving in a straight line at a constant velocity.

What key property is shared by two objects connected by a taut, unstretchable string?

Both connected objects experience the exact same magnitude of acceleration (a1 = a2 = a)

What is the general procedure for analyzing a system of connected objects?

Treat each object as an independent system by drawing a separate free-body diagram for each, then apply Newton’s second law (ΣF = ma) individually to solve for unknowns like acceleration and tension.

How should the coordinate system be defined to simplify the equations of motion?

Align the coordinate axes so that the coordinate direction bends along with the string over the pulley. This ensures a consistent positive direction for the motion of both objects.

A 100 kg fridge is pushed horizontally with 400 N against 294 N of friction. What is its horizontal acceleration?

Calculation: ∑Fx= Fpush- f = 400N - 294N =106 N ax= ∑Fx/m = 106N/100kg=1.06 m/sec².

What is the normal force supporting a 100kg object resting on a flat, horizontal floor? (Use g= 9.8 m/s²)

Calculation: in vertical equilibrium on a flat surface, N = W = mg = 100 kg x 9.8 m/s² = 980 N.

In what direction does the frictional force always act relative to motion?

Parallel to the contact surface and directly opposing the direction of actual or impending motion.

What are the 6 classic simple machines identified in mechanics?

1. lever

2. inclined plane

3. pulley

4. wedge

5. wheel and axel

6. screw

Why does the string tension remain constant across an ideal pulley?

an ideal pulley is massless and frictionless, allowing it to redirect the tension force without altering its magnitude along the string.