Unit 2 Force

Force – push or pull a force always acts in a certain direction ex. if you push something, the force is in the direction of the push

Forces in Nature Electric force ex. lightning Magnetic force ex. magnetic poles Gravity

Weight is a force

Newton metric unit of force

What is gravity? Sir Isaac Newton 1642 – 1727 The Principia

Gravity force of attraction between all objects in the universe

Gravity the larger an object’s mass, the greater the gravitational force

Gravity the greater the distance between two objects, the smaller the gravitational force the force of gravity decreases by the amount equal to one divided by the distance (d) squared 1/d 2

What is air resistance? air resistance force that opposes the movement of an object in air

Air Resistance a larger surface area usually results in greater air resistance lighter objects feel more air resistance than heavier objects

Terminal Velocity speed at which air resistance and gravity acting on an object are equal as an object falls, it’s speed increases at a steady rate until it reaches it’s terminal velocity

Vacuum – empty space in a vacuum, all objects fall at the same speed

What is friction? Friction force that opposes the motion of an object the force of friction works in the opposite direction of the force of motion

Types of Friction Sliding Friction the source of friction is the contact between two surfaces, at least one of which is in motion

Types of Friction Air Resistance friction results from air pushing on an object as it is moving

Types of Friction Rolling Friction friction between two surfaces that are not in constant contact ex. wheels

Friction friction makes motion possible friction also makes it hard to move objects reducing friction makes it easier to move objects

How can friction be reduced? by changing sliding friction into rolling friction by using lubricants Lubricants – substances that reduce friction

What is pressure? Pressure force per unit area

Pressure pressure is the amount of force acting on a surface pressure equals force divided by area p = f/a

Pressure pressure can be changed by changing the amount of force acting on an area pressure can be changed by changing the area on which a force acts

Fluid Pressure pressure in gases and liquids

Air Pressure air pressure is caused by the motion of particles in the air you do not feel the weight of the air because the pressure inside your body is equal to the air pressure around you

Air Pressure air pressure changes with altitude the higher you are, the lower the air pressure

Air Pressure Barometer instrument used to measure air pressure

Water Pressure the force of water pressure on an object is the same in all directions water pressure changes with depth the deeper you are, the greater the water pressure

Water Pressure Manometer instrument used to measure pressure in a liquid

What is Bernoulli’s principle? Bernoulli’s Principle principle that states that as the speed of a fluid increases, its pressure decreases

Bernoulli’s Principle airplane wings are designed to use Bernoulli’s principle air traveling over the wings moves faster than air underneath this reduces the pressure on top of the wing, allowing it to be pushed upward

Bernoulli’s Principle three forces combine to help an airplane fly the upward force on a plane’s wing is called lift a forward force, or thrust, helps the plane take off and maintain air speed the air resistance on a plane is called drag