Forces in Motion Chapter 2 Notes Part 1

Questions How does the force of gravity affect falling objects? What is projectile motion? What are Newton’s laws of motion? What is momentum?

Falling Objects Mass of an object does not affect the rate at which it falls. All objects fall with the same acceleration rate due to gravity. (9.8 m/s/s on Earth)

Air Resistance definition – fluid friction that opposes the motion of objects as they pass through the air. Acts to slow down acceleration. Will affects some objects more than others due to their size and shape.

Affects of air resistance on downward acceleration of a falling object The force of air resistance Net force on the object The force of gravity

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Terminal Velocity As speed the amount of air resistance As the object falls, upward forces of air resistance increases until they equal the downward force of gravity Net force is zero Objects stops accelerating Object falls at constant velocity, which is called its terminal velocity.

Free fall Occurs when there is no air resistance. Only force acting on the object is the force of gravity.

Orbiting Objects are in Free Fall Two motions combine to cause orbiting –Moving forward –Free fall toward Earth –Causes centripetal (center seeking) force

Projectile Motion definition: The curved path an object follows when thrown or propelled near the surface of the Earth.

Projectile Motion Caused by two independent forces: –Horizontal – the force applied to move it forward. Causes motion parallel to the ground. –Vertical – gravity pulling on the object. Causes motion perpendicular to ground.

Explain Explain why a ball moves in a straight lines as it rolls across a table but follows a curved path once it rolls off the edge of the table.

History of Newton’s Laws Sir Isaac Newton ( ) an English scientist and mathematician famous for his discovery of the law of gravity also discovered the three laws of motion. Today these laws are known as Newton’s Laws of Motion and describe the motion of all objects on the scale we experience in our everyday lives.

“ If I have ever made any valuable discoveries, it has been owing more to patient attention, than to any other talent.” - Sir Isaac Newton

Newton’s 3 Laws of Motion An object in motion tends to stay in motion and an object at rest tends to stay at rest unless acted upon by an unbalanced force. Force equals mass times acceleration (F = ma). For every action there is an equal and opposite reaction.

Momentum Momentum is a property of moving objects. Amount depends on the objects mass and velocity. Formula: p = m x v momentum = mass x velocity

Conservation of Momentum When two or more objects interact, momentum may be transferred, but the total amount of momentum does not change. This is known as the “ Law of Conservation of Momentum”.