Physics Unit: Force & Motion

Transcription

1 Physics Unit: Force & Motion What is physical science? A. Physical science is a field of science that studies matter and energy. B. Physical science has 2 main branches: 1. PHYSICS: the study of how matter and energy interact robotics, nuclear energy, solar panels 2. CHEMISTRY: the study of the structure, makeup, and changes of matter chemicals, acids & bases, medicines

2 What is energy? A. ENERGY: the ability to do work or make something happen B. All forms of energy fall under two categories: 1. POTENTIAL ENERGY: stored energy that could make something happen a. Chemical Energy b. Nuclear Energy c. Stored Mechanical Energy d. Gravitational Energy 2. KINETIC ENERGY: used energy that is making something happen a. Radiant Energy b. Thermal Energy c. Motion d. Electrical Energy e. Sound

3 What are the different forms of energy? A. There are many different forms of energy to make things happen. B. Below are 6 of the major forms: 1. MECHANICAL ENERGY: the energy in moving objects 2. ELECTRICAL ENERGY: energy from the flow of electrons 3. ELECTROMAGNETIC ENERGY: energy in the form electrical and magnetic waves that can travel through space 4. HEAT ENERGY: thermal energy that comes from moving particles of matter (friction) 5. CHEMICAL ENERGY: energy that holds particles of matter together (chemical bonds) 6. NUCLEAR ENERGY: energy stored in an atom s nucleus

4 What happens to energy? A. Energy is never lost, it only changes into another kind or form of energy. 1. Potential becomes kinetic and vice versa. a. Roller coaster moving from hill to hill 2. Chemical energy becomes electrical energy becomes light energy becomes heat energy a. Battery to electricity to a lit light bulb that gets hot B. LAW OF THE CONSERVATION OF ENERGY: energy can neither be created nor destroyed, only changed in form.

5 What is a wave? A. WAVE: a disturbance that transfers energy from one place to another. 1. A wave is energy traveling through a medium like particles of air or water 2. There are two major forms of waves: a. MECHANICAL WAVES: waves that travel through matter b. ELECTROMAGNETIC WAVES: waves that can travel through matter or empty space 3. All waves have 3 features in common: a. WAVELENGTH: the distance between one full wave to another b. FREQUENCY: the number of complete waves that pass a certain point per second c. AMPLITUDE: the height of a transverse wave or the amount of compression of a longitudinal wave

6 What is a wave? B. Waves that travel through matter can do it one of two ways: 1. TRANSVERSE WAVE: waves that move up and down a. There are two parts to a transverse wave i. CREST: the highest point of a wave ii. TROUGH: the lowest point of a wave b. A wavelength is from one crest to another c. Amplitude is the height of the crest 2. LONGITUDINAL WAVE: waves that move back and forth a. There are two parts to a longitudinal wave i. COMPRESSION: where the particles are close together ii. RAREFACTION: where particles are far apart b. A wavelength is from one compression to another c. Amplitude is the tightness or looseness of the compression

7 What is Light? A. LIGHT: a form of electromagnetic energy made up of streams of photons. 1. PHOTON: a very small bundle of energy 2. Light behaves like a transverse wave that can travel through matter or empty space 3. Light waves have four properties: a. The speed of light is 300,000 km/s in space b. The wavelength is measured from crest to crest c. Frequency is measured by the number of light waves that pass a certain point each second d. Amplitude is the height of the crest with bright light having taller crests and dim light having shorter crests

8 What is Light? B. When light interacts with matter or objects made of matter, the light will behave in different ways 1. Some objects can allow light to be transmitted, absorbed or reflected. a. TRANSMISSION: light passes through an object b. ABSORBTION: light is absorbed into an object c. REFLECTION: light bounces off an object 2. Some objects can be categorized as luminous or illuminated. a. LUMINOUS OBJECT: objects that give off light b. ILLUMINATED OBJECTS: objects that reflect light i. OPAQUE: objects that block light ii. TRANSPARENT: objects that allow light to pass through iii. TRANSLUCENT: objects that allow some light to pass through

9 What is Light? 3. Some matter can cause light to change the direction it is traveling as its transmitted a. REFRACTION: the bending of light when it passes from one transparent material to another b. LENS: a transparent material that refracts light inward or outward 4. Some matter has surfaces that allow a type of reflection that causes an image 1. Mirrors are examples of surfaces that reflect light causing an image

10 What is mechanical energy? A. MECHANICAL ENERGY: the energy an object has that causes it to move B. Mechanical energy can come in one of two ways: 1. STORED MECHANICAL ENERGY: potential mechanical energy that could cause an object to move 2. MOTION: kinetic mechanical energy that causes an object to move C. A force acting on an object is required for mechanical energy

11 What is a force? A. FORCE: a push or pull exerted on an object B. To describe a force, you must know a force s size and direction C. Size and direction can cause one of two situations: 1. BALANCED FORCES: forces on an object equal in size but opposite in direction 2. UNBALANCED FORCES: forces on an object that are no longer balanced, causing a change in the motion of an object

12 How is a force depicted, described, and measured? A. A force is often depicted with the use of arrows that come in various sizes. 1. Arrows show direction 2. Different sized arrows show how strong the force is B. Forces are often measured using instruments: 1. A spring scale is often used to measure a force, they measure a force using newtons 2. NEWTON: a standard unit of force depicted as an N 3 N 3 N 1 N 3 N 3 N 8 N

13 What is motion? A. Mo%on is kine%c mechanical energy that causes an object to move B. Mo%on is observed when an object changes its posi%on or loca%on as compared to something else that has a fixed posi%on 1. We know an object is in mo%on when it changes posi%on in an environment where other things aren t moving with it. 2. Car drives down the street and we no%ce it move away because we and other things aren t moving with it.

14 How is motion described? A. Motion can be described in terms of speed and direction: 1. VELOCITY: the speed and direction of a moving object a. Speed is a measurement of how fast an object is moving i. Distance in meters (m) ii. Time in seconds (s) b. Direction must be figured out using a compass to determine N, S, E, W, NE, NW, SE, SW, etc. B. Velocity can be written as a formula: 1. Distance Time & Direction = Velocity 2. Velocity is written in meters per second m/s a. m s & direc%on = m/s & direc%on C. When an object changes speed or direction, it is accelerating 1. ACCELERATION: a change in an object s velocity 2. Acceleration occurs when an object: a. Slows down or moves faster b. Changes the direction it is moving

15 What is Work? A. WORK: force exerted on an object that moves it over a measurable distance 1. Two things must be measured to determine work: a. Force in Newtons (N) b. Distance in meters (m) 2. If an object does not move, no work is accomplished. B. Energy can be defined as the ability to do work. 1. For work to be done, a force must make an object move. 2. If a force is exerted, but there is no movement then no work has been accomplished. C. Work can be written as a formula: 1. Force x Distance = Work 2. Work is written in Joules (J) a. a. JOULE: a unit of work equal to a force of 1 N that moves an object 1 m. b. N x m = J

16 What is Power? A. POWER: the amount of work done per unit of time 1. Power is the rate at which work is done 2. To determine power, two things must be measured: a. Work in Joules (J) b. Time in seconds (s) B. There is a formula for power: 1. Work Time = Power 2. WATT: a unit of power equal to 1 Joule of work per second

17 What is Momentum? A. MOMENTUM: a property of all moving objects where an object with greater mass and/or velocity will have greater mechanical energy B. mass x velocity = momentum (g x m/s = g m/s) 1. If two objects with the same mass are moving, the one with greater velocity has more mechanical energy 2. If two objects are moving with the same velocity, the one with greater mass has more mechanical energy. C. THE LAW OF THE CONSERVATION OF MOMENTUM: momentum of an object can be transferred to other objects but can not be lost

18 Which major forces affect the motion of objects? A. Gravity is one of the major forces acting on objects 1. GRAVITY: a force of attraction between all objects in the universe 2. An object has more pull if its made of more matter 3. An object has more pull if its closer to another object B. On Earth, objects are pulled to the center of the planet by the dense mass of the planet s core

19 Which major forces affect the motion of objects? C. Friction is another major force moving objects must contend with: 1. FRICTION: a force that pushes back on a moving object 2. This force often occurs when an object moves over or through another type of matter D. There are different types of friction: 1. STATIC FRICTION: friction an object must overcome to start moving 2. AIR RESISTANCE: friction an object experiences when moving through air 3. ROLLING FRICTION: friction between a surface and a circular object

20 Which major forces affect the motion of objects? E. Friction can aid in motion and slow or prevent motion: 1. The wheels of a bike must push against the road to begin moving (friction) 2. The tread on shoes must push against the floor to walk (friction) 3. A braking car must move against a surface to stop (friction) 4. A heavy box won t move across a course surface (friction) F. The level of friction on an object can be overcome or altered to move an object 1. A push or pull stronger than the force of friction will allow an object to move 2. Allowing an object to roll reduces the friction on that object 3. LUBRICANT: materials that reduce friction; like oil, ice, lotions, smooth surfaces, etc.

21 What is a Simple Machine? A. MACHINE: a device that makes work easier 1. A machine can make work easier in three ways: a. Reducing the size of the force b. Changing the direction of the force c. Changing the speed of the force 2. Most machines are a combination of two or more simple machines: a. LEVER b. INCLINED PLANE c. WHEEL & AXLE d. PULLEY e. SCREW f. WEDGE

22 What is a Simple Machine? B. Work is a force exerted on an object allowing the object to move a distance 1. When working with a machine there are two primary forces involved: a. EFFORT FORCE: the force applied to the machine to accomplish work b. RESISTANCE FORCE: the force of the object that opposes the effort force

23 What is a Simple Machine? C. Most machines make work easier by maximizing the effort force you apply to the machine. 1. MECHANICAL ADVANTAGE (MA): the number of times a machine multiplies the effort force a. Mechanical advantage determined using a formula: Resistance force Effort force = MA RF 25 N EF 5 N = 5 MA b. The greater the MA the more the machine is maximizing your effort force.

24 How do Levers Work? A. LEVER: a bar or plane that is free to pivot or turn around a fixed point 1. Three major parts of a lever: a. FULCRUM: the fixed point a lever pivots or turns around b. EFFORT ARM: the part of the bar from the effort force to the fulcrum c. RESISTANCE ARM: the part of the bar from the fulcrum to the resistance force

25 How do Levers Work? B. A lever does two things to make work easier: 1. Reduces the size of the effort force required 2. Changes the direc%on of the force C. There are three types or classes of levers based on the posi%on of the fulcrum, EF, and RF: 1. First class lever: the fulcrum is between the EF & RF (crowbar) 2. Second class lever: the RF is between the fulcrum & EF (wheelbarrow) 3. Third class lever: the EF is between the fulcrum & RF (shovel)

26 How do Wheel & Axles Work? A. WHEEL & AXLE: a circular object that turns around a fix point or rod 1. A wheel and axle reduces the amount of fric%on between the resistance and the surface it moves over. 2. The longer the radius (from axle to edge of wheel) the further the distance the wheel will move.

27 How do Wheel and Axles Work? B. Wheel & axles are parts of other simple machines: 1. Pulleys are a wheel and axle with a rope wrapped around it 2. Gears are special wheels with teeth able to bite and turn each other.

28 How Do Inclined Planes Work? A. INCLINED PLANES: a slanted surface or ramp 1. An inclined plane makes work easier by changing the angle you have to exert a force to liw an object. 2. The lesser the angle of an inclined plane, less force needs to be exerted.

29 How Do Inclined Planes Work? B. Inclined planes are parts of other simple machines: 1. A wedge is two planes back to back 2. A screw is an inclined planed wrapped around a cylinder.

30 What are Newton s Laws of Motion? A. Sir Isaac Newton is credited as the father of classic mechanics. He developed three laws of mo%on s%ll used today: 1. First Law of Mo%on: INERTIA: an object at rest or in mo6on will remain at rest or in mo6on at a constant speed on a straight path un6l acted upon by an unbalanced force 2. Second Law of Mo%on: the unbalanced force ac6ng on an object is equal to the object s mass 6mes its accelera6on (a force will cause a greater change in velocity on an object with less mass than one with greater mass) 3. Third Law of Mo%on: for every ac6on force, there is an equal and opposite reac6on force