Motion and Forces Moving things

Dress Code still applies in the Spring. Reminders Shorts, (past the end of your fingers by you side) Holes in jeans (nada) Straps need to be three fingers

Position and Motion Position = where something is in the world Examples: plot points, reference points (by the mailbox) Motion = a change in position of an object Relative motion

Speed Speed = rate of change in position. V = speed V= distance/time Unit = m/s

Types of Speed Instantaneous speed = rate of change at any given moment Ex. Speedometer in your car, radar gun Average speed = total distance traveled divided by total time.

Velocity Velocity = speed and direction (vector) Ex. Car moving around a curve may have same speed but different velocity because direction is changing. Unit = m/s South  s_sim/mfm05_pg31_acceleration/mfm05_pg31_ acceleration.html s_sim/mfm05_pg31_acceleration/mfm05_pg31_ acceleration.html

Acceleration Acceleration = rate of change of velocity Positive = increases, Negative = decreases Unit = m/s/s or m/s² Acceleration = final velocity – initial velocity time Ex. Ion engine to deep space reaches 62,900 miles per hour (30 kilometers per second)

Forces Forces change motion by pushing or pulling Some types of forces include: Contact Gravity Friction Force is a vector (thus size and direction)

Balance and unbalanced forces Net forces include all forces from all directions Balance forces mean no change in direction Unbalanced forces mean that something will change. Newton’s First Law – an object in motion (at rest) stays in motion (at rest) unless another force is acted upon it.

Inertia Resistance to change. An objects inertia is determined by it’s mass Ex. Body in a car crash without seatbelt. Centripetal Force – force that keeps an object moving in a circle (changes the direction toward the center of the circle)

Force and Mass determine acceleration Newton’s second law – Force = Mass x Acceleration  As acceleration in a rocket increases, what would happen to it’s Force? Would a bolt in orbit have much force when it hit a satellite?

Forces act in pairs Newton’s 3 rd law - For every action there is an equal and opposite reaction. For every action there is an equal and opposite reaction. Ex. Kangaroo jump, swim in molasses, push skaters

Forces transfer momentum Momentum = mass x velocity Any object in motion has momentum Collision = transfer of momentum Momentum is ALWAYS conserved Ex. Bumper cars vs. real cars; fireman vs. hose; billiard balls.

Gravity is a force exerted by masses Gravity is a pull between any two masses in the universe determined by mass and distance Calculation is F = m x g g = the constant acceleration of gravity Weight is the force of gravity on an object.

Projectile motion Horizontal motion and vertical motion don’t necessarily effect each other. (Ruler and washer mini- lab proves this) Ex. Baseball pitch has constant horizontal velocity due to inertia, increasing vertical velocity due to gravity.

Friction is a force that opposes motion Force that resists the motion between two surfaces in contact. Effects on friction: Friction is greater on non-moving surfaces Types of surfaces determine amount of friction Pressure pushing the surfaces together

Friction of fluids Fluids can reduce friction (Ex. Motor oil) Fluids can be the source of friction (Ex. Air resistance, drag) Terminal velocity is the point where friction to air balances with acceleration of gravity.

Pressure depends on force and area Pressure = Force / Area Unit = Pa (pascal) = 1N/m² Examples of uses: Thumbtack, snowshoes

Pressure for fluids In Fluids, pressure acts in all directions. (skin diver, submarines) Pressure can depend on depth. (Air on mountain, bottom of ocean) Each 33 ft of ocean depth = 1 atmosphere)

Fluids can exert a force on objects Buoyancy is a net force that offsets the weight/density of an object. Motion of a fluid affects pressure Bernoulli’s Principle – increase in speed of a fluid decreases it’s pressure within it (airplanes and prairie dogs) Pascal’s Principle outside pressure applied at any point in a container transmits the pressure throughout the fluid. (hydraulics jacks)