Chapter 13 Motion and Forces

Ch 13 Sec 1: Gravity Vocabulary gravity weight mass

Effects of Gravity All matter has mass Gravity = force of attraction Due to mass of objects

Effects of Gravity Gravity pulls objects together All objects exert gravity on other objects Some objects too small of mass to notice

Effects of Gravity Earth’s mass = pulls everything on planet to its center You must apply force to overcome gravity any time you lift

Newton and Gravity Falling apple Law of universal gravitation Concluded must be unbalanced force makes apple fall Law of universal gravitation

Law of universal gravitation Gravity depends on product (multiplication) of the masses of the objects Gravity depends on distance between objects

Weight & Gravity Mass = amount of matter in object Weight = amount of pull of gravity Gravity = same everywhere on Earth Gravity changes throughout universe depending on mass of nearest celestial body

Gravity & Static Objects Static objects balance gravity by tension or compression

Ch 13 Section 2: Gravity and Motion Terminal velocity Free fall Projectile motion

Gravity & Falling Objects Gravity affects acceleration equally Objects fall at same rate Acceleration is dependent on mass and force heavier objects = greater gravitational force But heavier objects = harder to accelerate due to more mass

Gravity & Falling Objects All falling objects on Earth accelerate at 9.8 m/s²

Air Resistance & Falling Air resistance = force opposes gravity Its magnitude depends on Size Shape Speed of object

Air Resistance & Falling Terminal velocity falling speed when velocity no longer changes Speed is same Direction same

Air Resistance & Falling Free Fall = only gravity acting on falling object No air resistance only possible in a vacuum

Projectile Motion Two separate movements Horizontal vertical

Projectile Motion Horizontal movement Vertical Movement Force gives object horizontal movement Throwing a ball Vertical Movement Gravity pulls downward Gravity only affects vertical movement

Orbiting Gravity provides centripetal force for an orbit Centripetal = towards the center Gravity = force to keep solar system in order

Ch 13 Sec 3: Newton’s Laws Vocabulary inertia

Newton’s 1st Law An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force

Newton’s 1st Law Friction Common force to stop object in motion

Newton’s 1st Law Sometimes called Law of Inertia Inertia = at rest, stays at rest Inertia & mass related Smaller mass = less inertia Larger mass = more inertia

Newton’s 2nd Law of Motion The acceleration of an object depends on mass of the object and the amount of force applied

Newton’s 2nd Law of Motion Acceleration depends on mass more mass, with same force = less acceleration Less mass, same force = greater acceleration

Newton’s 2nd Law of Motion Acceleration depends on force Less force, same mass= less acceleration More force, same mass = greater acceleration

Newton’s 3rd Law of Motion Whenever one object exerts a force on a second object, the second objects exert an equal and opposite force on the first

Newton’s 3rd Law of Motion Action / Reaction Forces act in pairs