Unit 2: Motion & Forces September 25 - October 18 (18) Useful websites
All things in the universe are in constant motion. Describing, measuring, and predicting that motion may seem like rocket science at times, but the principles are fairly simple. From defining terms and filling in formulas to testing the real-world applications of these principles, this unit involves both exploration and imagination. Taking the obvious for granted may not be as easy for you as it once was.
Chapter 5 --Matter in Motion (measuring motion / what is a force? / friction / gravity) (my notes)
Chapter 6 --Forces and Motion (gravity and motion / Newton's laws of motion / momentum) (my notes)
Chapter 7 --Forces in Fluids (fluids and pressure / buoyant force / fluids and motion) (my notes)
Unit 2: Forces and Motion
Section 1: Measuring Motion
Objectives
Describe the motion of an object by the position of the object in relation to a reference point
Identify the two factors that determine speed
Explain the difference between speed and velocity.
Analyze the relationship between velocity and acceleration.
Demonstrate that changes in motion can me measured and represented on a graph.
Vocabulary
motion, speed, velocity, acceleration
Sections
Observing Motion by Using a Reference Point (118)
Speed Depends on Distance and Time (119)
Velocity: Direction Matters (120)
Acceleration (121)
Summary
An object is in motion if it changes position over time in relation to a reference point
Speed is the distance traveled by an object divided by the time the object takes to travel that distance.
Velocity is speed in a certain direction
Acceleration is the rate at which velocity changes
An object can accelerate by changing speed, direction, or both
Speed can be represented on a graph of distance versus time
Section 2: What Is a Force?
Objectives
Describe forces, and explain how forces act on an object
Determine the net force when more than one force is acting on an object
Compare balanced and unbalanced forces
Describe ways that unbalanced forces cause changes in motion.
Vocabulary
force, newton, net force
Sections
Forces Acting on Objects (124)
Determining Net Forces (125)
Balanced and Unbalanced Forces (126)
Summary
A force is a push or a pull. Forces have size and direction and are expressed in newtons
Forces is always exerted by one object on another object
Net force is determined by combining forces. Forces in the same direction are added, forces in opposite directions are subtracted.
Balanced forces produce no change in motion. Unbalanced forces produce a change in motion.
Section 3: Friction: A Force that Opposes Motion
Objectives
Explain why friction occurs
List the two types of friction and give examples of each
Explain how friction can be both harmful and helpful
Vocabulary
friction
Sections
The Source of Friction (128)
Types of Friction (130)
Friction: Harmful and Helpful (131)
Summary
Friction is a forces the opposes motion
Friction is caused by hills and valleys on the surfaces of the two objects touching each other.
The amount of friction depends on factors such as the roughness of the surfaces and the force pushing the surfaces together.
Two kinds of friction are kinetic friction and static friction.
Section 4: Gravity: A Force of Attraction
Objectives
Describe gravity and its effect on matter
Explain the law of universal gravitation
Describe the difference between mass and weight.
Vocabulary
gravity, mass, weight
Sections
The Effect of Gravity on Matter (134)
Newton and the Study of Gravity (135)
The Law of Universal Gravitation (136)
Weight as a Measure of Gravitational Force (138)
Summary
Gravity is a force of attraction between objects that is due to their masses
The law of universal gravitation states that all objects in the universe attract each other through gravitational force.
Gravitational force increases as mass increases.
Gravitational forces decreases as distance increases
Weight and mass are not the same. Mass is the amount of matter in an object. Weight is the measure of the gravitational force on an object.
Lab: Detecting Acceleration
Have you ever noticed that you can “feel” acceleration? In a car or in an elevator, you may notice changes in speed or direction- even with your eyes closed! You are able to sense these changes because of tiny hair cells in your ears. These cells detect the movement of fluid in your inner ear. The fluid accelerates when you do, and the hair cells send a message about the acceleration to your brain. This message allows your to sense the acceleration. In this activity , you will build a device that detects acceleration. This device is called an accelerometer.
Section 1: Gravity and Motion
Objectives
Explain the effect of gravity and air resistance on falling objects
Explain why objects in orbit are in free fall and appear to be weightless
Describe how projectile motion is affected by gravity
Vocabulary
terminal velocity, free fall, projectile motion
Sections
Gravity and Falling Objects (150)
Air Resistance and Falling Objects (152)
Orbiting Objects Are in Free Fall (153)
Projectile Motion and Gravity (155)
Summary
Gravity causes all objects to accelerate toward Earth at a rate of 9.8 m/s2.
Air resistance slows the acceleration of falling objects. An object falls at its terminal velocity when the upward force of air resistance equals the downward force of gravity.
An object is in free fall if gravity is the only force acting on it.
Objects in orbit appear to be weightless because they are in free fall.
A centripetal force is needed to keep objects in circular motion. Gravity acts as a centripetal force to keep objects in orbit.
Projectile motion is the curved path an object follows when thrown or propelled near the surface of Earth.
Projectile motion has two components- horizontal motion and vertical motion. Gravity affects only the vertical motion of projectile motion.
Section 2: Newton’s Laws of Motions
Objectives
Describe Newton’s fist law of motion, and explain how it relates to objects at rest and objects in motion.
State Newton’s second law of motion, and explain the relationship between force, mass, and acceleration.
State Newton’s third law of motion, and give examples of force pairs.
Vocabulary
inertia
Sections
Newton’s Laws of Motion (158)
Newton’s Second Laws of Motion (161)
Newton’s Third Law of Motion (163)
Summary
Newton’s first law of motion states that the motion of an object will not change if no unbalanced forces act on it.
Objects at rest will not move unless acted upon by an unbalanced force.
Objects in motion will continue to move at a constant speed and in a straight line unless acted upon by an unbalanced force.
Inertia is the tendency of matter to resist a change in motion. Mass is a measure of inertia.
Newton’s second law of motion states that the acceleration of an object depends on ist mass and on the force exerted on it.
Newton’s second law is represented my the following equation: F = m x a
Newton’s third law of motion states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.
Section 3: Momentum
Objectives
Calculate the momentum of moving objects.
Explain the law of conservation of momentum.
Vocabulary
momentum
Sections
Momentum, Mass, and Velocity (166)
The Law of Conservation of Momentum (167)
Summary
Momentum is a property of moving objects
Momentum is calculated by multiplying the mass of an object by the object’s velocity.
When two or more objects collide, momentum may be transferred, bu the total amount of momentum does not change. This is the law of conservation of momentum.
Lab: Intertia-Rama!
Inertia is a property of all matter, from small particles of dust to enormous planets and stars. In this lab, you will investigate the inertial of various shapes and kinds of matter. Keep in mind that each investigation requires you to either overcome or use the object’s inertia.
Section 1: Fluids and Pressure
Objectives
Describe how fluids exert pressure.
Analyze how atmospheric pressure varies with depth.
Explain how depth and density affect water pressure.
Give examples of fluids flowing from high to low pressure.
Vocabulary
fluid, pressure, pascal, atmospheric pressure
Sections
Fluids Exert Pressure (180)
Atmospheric Pressure (181)
Water Pressure (183)
Pressure Differences and Fluid Flow (184)
Summary
A fluid is any material that flows and takes the shape of its container.
Pressure is force exerted on a given area.
Moving particles of matter create pressure by colliding with one another and with container walls
The pressure caused by the weight of the atmosphere is called atmospheric pressure
Fluid pressure increases as depth increases
As depth increases, water pressure increases faster than atmospheric pressure because water is denser than air.
Fluids flow from areas of high pressure to areas of low pressure.
Section 2: Buoyant Force
Objectives
Explain the relationship between fluid pressure and buoyant force.
Predict whether an object will float or sink in a fluid.
Analyze the role of density in an object’s ability to float.
Explain how the overall density of an object can be changed.
Vocabulary
buoyant force, Archimedes principle
Sections
Buoyant Force and Fluid Pressure (186)
Weight Versus Buoyant Force (187)
Floating, Sinking, and Density (188)
Changing Overall Density (189)
Summary
All fluids exert an upward force called buoyant force.
Buoyant force is caused by differences in fluid pressure.
Archimedes’ principle states that the buoyant forces on an abject is equal to the weight of the fluid displaced by the object.
Any object that is more dense than the surrounding fluid will sink. An object that is less dense than the surrounding fluid will float.
The overall density of an object can be changed by changing the object’s shape, mass, or volume.
Section 3: Fluids and Motion
Objectives
Describe the relationship between pressure and fluid speed.
Analyze the roles of lift, thrust, and wing size in flight.
Describe drag and explain how it affects lift.
Explain Pascal’s principle.
Vocabulary
Berboulli’s principle, lift, thrust, drag, Pascal’s principle
Sections
Fluid Speed and Pressure (192)
Factors that Affect Flight (193)
Drag and Motion in Fluids (195)
Pascal’s Principle (196)
Summary
Bernoulli’s principle states that fluid pressure decreases as the speed of the fluid increases
Wing shape allows airplanes to tae advantage of Bernoulli’s principle to achieve flight.
Lift on a airplane is determined by wing size and thrust.
Drag opposes motion through fluids.
Pascal’s principle states that a change in pressure in an enclosed fluid is transmitted equally to all parts of the fluid.
Videos: Atmospheric Pressure: Science online (5:11), History of Barometer (4:45), Egg into Bottle (3:05), Balloon (lung) in a Bottle (2:37), 10 Experiments (9:12),
Gravity: Warping of Space-Time,
Lab: Fluids, Force, and Floating
Why do some objects sink in fluids by others float? In this lab, you will get a sinking feeling as you determine that an object floats when its weight equals the buoyant force exerted by the surrounding fluid .