Topic 8 - Intro to Forces & Newton's Laws of Motion

Question 1

Classical Mechanics

Answer 1

Describes the relationship between the motion of objects found in our everyday world and the forces acting on them

Kinematics: study of motion of objects without regard to the forces that cause the motion

Dynamics: study of how forces affect the motion of objects

Question 2

What are forces?

Answer 2

Can think of it as a “push” or “pull” on an object

Imagined as a push or pull on some object, typically in a rapid manner

Usually a force is applied to an object, which give changes its kinematic properties (velocity, acceleration)

Question 3

Types of Forces

Contact Force

Answer 3

Comes from physical
contact from force to object

• Pulling, Kicking, Ground, Friction, etc

Question 4

Types of Forces

Field Force

• Typically known as fundamental forces
• In order of decreasing strength: strong nuclear force (subatomic particles), electromagnetic forces, weak nuclear forces (radioactive decay), gravitational force

Answer 4

Comes from an invisible influence

• Gravitational Attraction, Electric Fields, Magnetic Fields

Question 5

Newton’s First Law of Motion

If there are no external forces acting on an object, the object’s existing motion (or lack of motion) remains unchanged

Answer 5

An object at rest remains at rest, and an object in motion remains in motion at constant speed and direction unless acted on by a nonzero net force

* Internal forces are not included

• Net Force = vector sum of all external forces exerted on the object

Question 6

Newton’s Second Law of Motion

Answer 6

The acceleration of an object is directly proportional to the net force acting
on it and inversely proportional to its mass

• To solve questions, we need to be able to resolve components again into 𝐹𝑥, 𝐹𝑦

Question 7

Newton’s Third Law of Motion

Answer 7

When one object exerts a force on another object, the second object exerts and equal and opposite force on the first object

Question 8

Terminology used in Forces

Answer 8

Question 9

Problem Solving Approach to 1D Kinematics

Answer 9

1. Read the question and highlight was your end goal is (what you’re trying to find)
2. Always set a frame of reference and what direction is positive
3. Draw a diagram and label all important forces
4. Make a list of all known/unknown variables
5. Apply Newton’s Laws of Motion and solve

Question 10

Key Concepts

Answer 10