Ch 2 Newtons laws of Motion

Chapter 2: Newton's Laws of Motion

Overview

• Focus on understanding:

  • Newton’s First Law of Motion

  • Newton’s Second Law of Motion

  • Forces and Interactions

  • Newton’s Third Law of Motion

  • Summary of Newton’s Three Laws

Newton’s First Law of Motion

Definition

• Also known as the law of inertia:

  • Every object remains at rest or continues to move in a straight line with constant speed unless acted upon by a nonzero force.

Examples and Implications

• A sheet of paper can be pulled from under a soft-drink can without toppling due to the can's inertia.

• If a stone swung in a horizontal circle has its string broken, it will continue in a straight line path

• Inertia can be observed in various scenarios, like the behavior of coins, hammers, and in high-speed environments like airplanes.

Newton’s Second Law of Motion

Definition

• This law explains the relationship between force, mass, and acceleration:

  • Acceleration is produced by a net force and is directly proportional to that force and inversely proportional to the mass.

Equation

• The mathematical formula is:

  • a = F/mwhere:

    • a = acceleration

    • F = net force

    • m = mass

Practical Examples

• If the mass of an object decreases while the force applied stays constant, the acceleration will increase.

• During free fall, an object accelerates towards Earth at approximately 10 m/s², unaffected by mass when air resistance is negligible.

• Multiple scenarios, such as comparing falling objects with different masses, demonstrate that all objects accelerate equally regardless of weight in a vacuum.

Terminal Velocity

• As an object falls, it will eventually reach terminal velocity when gravitational force equals air resistance, resulting in no acceleration.

• An example is a skydiver where air resistance increases until it balances with the weight of the diver, preventing further acceleration.

Newton’s Third Law of Motion

Definition

• Known as the law of action and reaction:

  • For every action, there is an equal and opposite reaction.

Applications

• When one object exerts a force on another, the second object exerts an equal force in the opposite direction.

• Examples include a soccer player kicking a ball (equal force exerted back to the foot) and the mutual forces experienced when jumping off a curb (Earth and the person pulling on each other).

External and Internal Forces

• The effects of forces can vary depending on mass; higher mass results in smaller acceleration under the same force.

• If two equal masses push off from each other on ice, they will move with equal speeds in opposite directions due to equal and opposite forces.

Key Terms

• Free fall: Movement solely under the influence of gravitational pull.

• Terminal Speed: The constant speed reached when air resistance balances gravitational pull.

• Force Vector: Represents force magnitude and direction as an arrow.

• Velocity Vector: Represents velocity magnitude and direction.

• Resultant: Net effect of combining two or more vectors.

• Vector Components: Parts of a vector acting in different directions.