Presentation on theme: "Page 11 S8P3a. Motion 8/28/12 What are the similarities and differences between speed and velocity? Speed is the rate that an object moves. (How fast something."— Presentation transcript:
1Page 11S8P3a.Motion8/28/12What are the similarities and differences between speed and velocity?Speed is the rate that an object moves. (How fast something moves)Speed is measured in meters per second (m/s), kilometers per hour (km/hr) and miles per hour (mph)Speed is useful for knowing how fast vehicles move, how fast people run, etcSpeed is calculated by dividing the distance traveled by the time it takes to travel the distance.Speed = distance / time
2SPEED AND VELOCITY ARE NOT THE SAME Page 13Velocity is the rate that an object moves in a particular direction.Velocity is measured in meters per second (m/s), Kilometers per hour (km/hr) and miles per hour (mph) with a direction. For example:40 m/s westVelocity is useful for airplanes, helicopters and boats.Velocity is calculated by dividing the distance traveled by the time it takes to travel the distance.Velocity = distance / timeSPEED AND VELOCITY ARE NOT THE SAME
3On page 12 of your INB, make two columns and categorize the following descriptions as speed or velocity:car moving at 35mph bird flying at 40mph north jogger running at 10m/s jogger running at 10m/s southa vehicle racing at 125mphSpeedVelocity
4Page 15S8P3a.Motion9/5/12What is the relationship between velocity and acceleration?Acceleration is the rate at which an object’s velocity changes.There are 3 ways that acceleration can occur:speeding up (acceleration or positive acceleration)slowing down (deceleration or negative acceleration)Changing directionAcceleration is expressed in units like meters per second squared (m/s2)The formula for calculating acceleration is:Average acceleration= final velocity-initial velocitytimeSummary
5On the top half of pg.14 of your Science NoteBook Identify which is an example of acceleration and which is not:A train traveling 65 miles per hour northA boat sailing west at 5 knotsA person jogging at 3 meters/second along a curved pathA car stopped at a stop lightA car stopping at a stop lightA truck speeding up from 55mph to 75mphA person jogging at a constant speed along a straight pathAccelerationNot Acceleration
6On the bottom half of pg.14 of your Science NoteBook Complete the practice acceleration problems provided and paste into bottom half of page 14 leaving room for a summary.
7On the top of pg.16 of your Science NoteBook Write the following standard neatly.S8P3b. Students will demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia and friction
8S8P3b. Forces 9/7/12 How are forces related to the motion of objects? Page 17S8P3b.Forces9/7/12How are forces related to the motion of objects?All motion is due to forces acting on objects. A force is a push or pull. Force is measured in a unit called Newtons (N).The net force is a total combination (sum) of all forces acting on an object.A balanced force is one in which the net forces equal zero. There is no motion.An unbalanced force has a net force greater than zero. The object acted on shows movement in one direction. Only an unbalanced force can change the motion of an object.
9On the bottom of pg.16 of your Science NoteBook Underneath the standard
10S8P3b. Forces 9/10/12 How are forces related to the motion of objects? Page 19S8P3b.Forces9/10/12How are forces related to the motion of objects?An unbalanced force acting on an object at rest will cause it to __________________.An unbalanced force that acts on an object already in motion can change the speed OR direction of an object.Unbalanced forces can act in the same direction or in opposite directions. If forces are in the same direction, you add them. If forces are acting in the opposite direction, you subtract them.Summary
11During the game of tug-of-war On pg.18 of your Science NoteBookDuring the game of tug-of-warWhat happens when the two teams pull with equal force?What type of forces are these called?How would you represent this with force arrows?What happens when one team pulls with a greater force?How would you represent this with force arrows and an illustration?
12Page 21S8P3b.Forces9/17/12How are forces in nature related to the motion of objects?There are many different types of forces in nature that act on objects. They include: gravity, friction and inertia.Gravity is an attractive force that works to pull objects together.The law of universal gravitation states that a force of gravity acts between all objects in the universe.There are two factors that affect the force of gravity between objects: 1. the objects’ masses and 2. the distance between them. (mass is the amount of matter in an object).
13Page 23S8P3b.Forces9/17/12How are forces in nature related to the motion of objects?The larger the mass, the more the gravitational attraction.The shorter the distance between the objects, the more the gravitational attraction.Inertia is the tendency of an object to resist a change in motion.Mass affects inertia. An object with a large mass has more inertia than an object with a small mass.Summary
14On page 20Draw/write the following 3 questions and determine which has a greater gravitational “pull” and WHY.2.3.25kg35kg25kg5kg25kg25kgSet A (red balls)25kg25kgSet B (green balls)
15Earth On page 22 Moon Actual Orbit Inertia GravityMoonActual OrbitInertiaGravity and inertia work together to keep the Moon orbiting Earth. First, the Moon’s inertia pushes it to travel continuously in a straight line. At the same time, Earth’s gravity is pulling the Moon toward Earth. These combined forces cause the Moon to move in a curved path (orbit) around Earth. Without gravity, the Moon would fly off into space. The Moon is able to continuously orbit Earth because the Moon’s inertia and the Earth’s gravity are balanced.
16Question 1What happens to the motion of an object when the forces are balanced?A. The motion changes.B. The motion does not change.C. The motion speeds up.D. The motion slows down.
17Question 2What happens to an object if the forces acting upon it are unbalanced?A. Its motion will not change.B. The motion will come to a stop.C. The net force will be zero.D. Its motion will change.
18Question 3What happens to an object moving in the same direction as the net force?A. It will speed up.B. Its motion will not change.C. It will stop moving.D. It will slow down.
19Question 4Which pair of objects will have the greatest gravitational attraction to each other?A. two cinder blocks 6 centimeters apartB. two marbles 12 centimeters apartC. a cinder block and marble 6 centimeters apartD. a cinder block and marble 12 centimeters apart
20Page 25S8P3b.9/19/12Laws of MotionSince gravity works to pull objects toward each other, what keeps the planets from crashing into the Sun?Newton’s first law of motion states that an objects at rest will stay at rest, and an object in motion will continue in motion in a straight line unless an unbalanced force acts on the object.This law is sometimes called the Law of Inertia.This means if the net force acting on an object is zero, the object remains at rest, or if the object is already moving, continues to move in a straight line with constant speed.Summary
21Page 27S8P3b.9/19/12Laws of MotionIf Newton’s first law of motion is accurate, why do moving objects sometimes come to a stop?The force that brings nearly everything to a stop is called friction.Friction is the force that opposes the motion of an object. This contact force acts whenever an object in motion rubs against a surface. Friction opposes motion when two surfaces touch. The contact reduces the speed of the moving object and releases heat.There are 3 types of friction: sliding friction, rolling friction and static friction
22Page 29S8P3b.9/20/12Laws of MotionIf Newton’s first law of motion is accurate, why do moving objects sometimes come to a stop?Sliding friction is friction that slows down an object that slides. Example: brake pads on a bicycle that rub against the wheelStatic friction is friction that acts on an object at rest. Example: trying to move a refrigeratorRolling friction is friction that acts when an object rolls across a surface. Example: rolling a cart aroundSummary
23On page 26Draw an illustration of friction in action. Your illustration must be neat and colored. You must identify the two surfaces that are interacting and what is occurring in order for it to be friction. You must also identify the type of friction.
24Illustration with Labels On page 28Identify an example of each type of friction (not those provided in class). Illustrate, color and label the friction interaction of each using the table format below.Type of FrictionExampleIllustration with Labels
25Page 31S8P3b.9/25/12Newton’s lawsWhat is the relationship between force, mass and acceleration?Newton’s second law of motion states that the acceleration of an object depends on the mass of the object and the amount of force applied.This law can be expressed mathematically with:Force = mass x acceleration(newton) = (kilogram) x (meters/second2)Summary
26Write the question and answer: On page 30Write the question and answer:Name two ways to increase the acceleration of an object.1.2.What force is necessary to accelerate a 1,250kg car at a rate of 40m/s2?
27Page 33S8P3b.9/25/12Laws of MotionWhen a person pushes on a wall, the wall pushes back. How does this relate to Newton’s 3rd law?Newton’s third law of motion states that for every action there is an opposite and equal reaction. Forces act in equal and opposite pairs.Example: pushing on a wall, a rocket launching, diving off the side of a pool.Summary
28Page 35S8P3c.9/27/12Simple MachinesWhat is a simple machine and how do they make work easier?Work is the application of a force to an object to move a certain distance in the direction of the force.Work requires two things:a force applied to an objectthe object must move in the direction of the force.Example: pushing a lawnmowerThe equation for work is:work = force x distanceThe unit for work is the Joule (J).
29Page 37S8P3c.9/27/12Simple MachinesWhat is a simple machine and how do they make work easier?A simple machine is a device that makes work easier by changing the size of a force OR changing the direction of a force.The six simple machines are:PulleyInclined planeWedgeWheel and AxleScrewLeverSummary
30On page 34An inclined plane is a straight, slanted surface. They make work easier because it is easier to push an object up a ramp than to lift the same object straight up to the same height. Ex. a ramp
31On page 34A wedge is an inclined plane that is wider or thicker at one end than at the other. A wedge makes work easier because when moved, a wedge is used to cut, split, or pry apart objects. Ex. knife blade or axe.
32On page 34A screw is an inclined plane that is wrapped around a cylinder. When a screw is turned, a small force is applied over the long distance of the screw’s threads.
33On page 36A lever is a simple machine that consists of a bar that pivots at a fixed point called a fulcrum. The force applied to a lever is called the effort. The object being moved is called a load. There are three classes of levers: 1st class, 2nd class and 3rd class.
34On page 38A wheel and axle is a simple machine that consists of a shaft called the axle, inside the middle of a wheel. Ex. bicycle wheelAny force that is applied to the wheel gets transferred to the axle and vice versa. When force is applied to the wheel, the difference in size between the wheel and axle causes the force to increase as it is transferred to the axle.
35There are 2 kinds of pulleys: fixed and movable. On pages 38-39A pulley is a rope or chain wrapped around a wheel. A load is attached to one end of the rope. A force is applied to the other end of the rope.There are 2 kinds of pulleys: fixed and movable.A fixed pulley is one that does not move. They are often used to lift something. A fixed pulley changes the direction of force, but does not reduce the amount of force needed to lift the load.
36On pages 38-39A movable pulley is a pulley that moves. One end of the rope is tied to a stationary object and the other is free for you to pull on. The load is attached directly to the pulley. The pulley moves along the rope as the free end is pulled. They reduce the amount of force needed to move an object, but you must pull the rope farther.
37A block and tackle is a system (combination) of pulleys. On pages 38-39A block and tackle is a system (combination) of pulleys.
38Mechanical advantage = output force (Newtons) input force (Newtons) On pages 38-39Mechanical advantage = output force (Newtons)input force (Newtons)MA = F outF inEfficiency = output work (joules) X %input work (joules)Eff = W out X %W in