- Slides: 93
Amusement Park Forces
What is Motion? Motion: A change in position of an object compared to a reference point Motion involves all of the following:
Definition of Motion Event that involves a change in the position or location of something.
Motion is Relative I. Relative – it is described or compared to a REFERENCE POINT II. http: //www. amnh. org/education/resources/ card_frame. php? rid=937&rurlid=894 Example: Are you moving at this moment? If yes, then how are you moving? IV. How does your movement look to another person? (Can they tell you are moving? ) III.
Displacement vs Distance I. Displacement the distance and direction of an object’s change in position from its starting point I. Distance – how far something moves
What is the Displacement? I. Problem - A physics teacher walks 4 meters east, 2 meters south, 4 meters west, and 2 meters north. What is the total displacement of the teacher? III. What is the total distanced walked by the teacher? II.
And the answer is. . . I. Displacement = 0 The teacher has returned to the starting point. I. Distance = 12 meters II. The distance is 12 meters displacement is zero. The has “covered 12 meters ground”, yet when he is walking, he is not walking place. but the teacher on the finished out of
Types of Motion Uniform motion - constant speed in a straight line II. Accelerated motion – motion that is changing in speed or direction III. Circular motion - speed is constant but the direction of motion is changing continuously I.
What is Motion? Speed The rate of change in position Speed = distance ÷ time or Speed = distance time
Speed Types of Speed I. Average Speed I. Instantaneous Speed I. Constant Speed
Speed Average Speed Comparison of time and distance I. Distance traveled per unit time Distance is referring to "how much ground an object has covered" during the time it was in motion. A. B. 1. 2. 3. S=d/t T=d/s D=sxt
Speed Instantaneous Speed I. Speed at any instant
Speed Constant Speed that does not change I. A. Instantaneous speed that does not change A. Example: After setting cruise control on a car, your speed at any point will be the same until you turn off the cruise control.
What is Motion? Velocity Speed plus direction Example: 50 km/hour north
Velocity I. Speed AND direction -- Velocity must include a speed and a direction. Displacement is "how far out of place an object is because of its motion”. Displacement is the object's change in position.
What is Motion? Acceleration The rate of change in velocity Positive acceleration = speeding up Negative acceleration = slowing down (decelerate) Acceleration = Vfinal – Vinitial Time Acceleration = ∆Velocity Time or
Acceleration "the rate at which an object changes its velocity. " An object is accelerating if it is changing its velocity.
Acceleration I. A change in velocity A. Speeding up 1. Positive acceleration B. Slowing down 1. Negative acceleration 2. Deceleration C. Changing direction
The Direction of Acceleration will always have a direction associated with it. The direction of acceleration depends on two things: whether the object is speeding up or slowing down II. whether the object is moving in the + or - direction I.
Circular Motion: Continuous Acceleration An object traveling in a circular motion is always changing its direction. Therefore, its velocity is always changing, so it is accelerating. This is known as centripetal acceleration.
Motion Graphs Time – Distance Graphs
Motion Graph # 1 Straight, Flat Line I. As time passes, there is no change in distance; no motion
Motion Graph # 2 Straight, Increasing Line I. II. As time passes, distance increases The change in distance is constant – no stopping & starting
Motion Graph # 3 Straight, Decreasing Line I. II. As time passes, distance decreases The change in distance is constant
Motion Graph # 4 Changing Line I. II. A changing line means changing distance Distance increases then doesn’t change then decreases
Representing Motion in Graphs Distance – Time Velocity - Time
Describing a Distance - Time Graph
Describing a Velocity - Time Graph
Speed, Distance, Time Formulas
Calculating Speed Given Distance & Time Divide Distance by Time Divide Distance ÷ Time ÷= Time Speed= Speed =Speed Distance ÷ Time = Distance
Calculating Distance Given Speed & Time Multiply Speed and Time Distance = Speed X Time = Distance
Calculating Time Given Distance and Speed Divide Distance by Speed Distance ÷ Speed = Time = Distance ÷ Speed
What is a Force? FORCE = Any push or pull which causes something to move or change its speed or direction
What is a Force? Forces can be BALANCED or UNBALANCED Balanced forces are equal in size and opposite in direction Balanced forces are not equal in size and/or opposite in direction. If the forces on an object are UNBALANCED, we say a NET force results. Amusement Park Forces
What is a Force? May cause acceleration or changes in motion I. A. B. 1. 2. C. D. II. More than one force can act on an object at a time. The forces can push or pull in any direction. What happens to the object when the forces act depends on two things: How strong the forces are The direction of the forces When more than one force acts on an object, the forces combine to form a net force. The combination of all the forces acting on an object is the net force. Forces may work together or they may be opposite forces.
What is a Force? Can you think of examples of forces? Balanced Forces? Unbalanced Forces?
Balanced Forces I. III. IV. All forces acting on an object are equal There is no motion. Two or more opposite forces are balanced forces if their effects cancel each other and they do not cause a change in an object's motion. If two forces, of equal strength, act on an object in opposite directions, the forces will cancel, resulting in a net force of zero and no movement.
Unbalanced Forces I. III. IV. All forces acting on an object are not equal One or more force is stronger than others, motion occurs If the effects of the forces don't cancel each other, if one force is stronger than others, the forces are unbalanced forces. Unbalanced forces cause a change in motion; speed and/or direction.
Net Force I. Net Force - The sum of all forces acting on an object A. A net force of 0 1. No motion B. A net force of more than 0 1. Motion occurs
NET FORCE • When two forces act in the same direction on an object, the net force is equal to the sum of the two forces. • When two unequal forces act in opposite directions on an object, the net force is the difference of the two forces.
200 N 100 N • The forces shown above are PUSHING / PULLING forces. • The forces shown above are WORKING TOGETHER / OPPOSITE FORCES. • The forces are EQUAL / NOT EQUAL. • The forces DO / DO NOT balance each other. • The stronger force is pulling to the RIGHT / LEFT. • The weaker force is pulling to the RIGHT / LEFT. • Motion is to the RIGHT / LEFT.
What is Gravity? GRAVITY: GRAVITY An attraction force between all masses Newton’s universal law of gravitation: gravitation Every object in the universe exerts a gravitational attraction to all other objects in the universe The amount of gravitational force depends upon the mass of the objects and the distance between the objects
What is Gravity? The greater the mass, the greater the force The greater the distance, distance the less the force Acceleration due to gravity = 9. 8 m/s/s or 9. 8 m/s 2 Gravity in Space
Weight is a measure of the gravitational force between two objects The greater the mass the greater the force (weight) Measured in units called Newtons (N)
Weightlessness – free from the effects of gravity
What is Friction? Friction = A force that opposes or slows down motion Caused by the physical contact between moving surfaces The amount of friction depends upon the kinds of surfaces and the force pressing the surfaces together Changes motion into heat
What is Friction? Two Types of Friction I. Kinetic Friction- Friction between two moving objects- Sliding or Rolling A. We use sliding friction when we apply the brakes on a bike. B. We use rolling friction when we move anything on wheels. II. Static Friction- is applied to an object but does not cause the object to move
Ways to Reduce Friction Lubricants- applied to surface to reduce friction between surfaces ex. Oil, wax, grease II. Switch from sliding friction to rolling friction will reduce the amount of friction. III. Making surfaces smoother I.
Ways to Increase Friction Making surfaces rougher ex. using sand on icy roads II. Increasing the force pushing the surfaces together ex. Scrubbing a pan I.
What is Friction? What are some ways athletes uses friction?
Air resistance: The force of air exerted on a falling object The air pushes up as gravity pulls down Dependent upon the shape and surface area of the object When the air resistance equals the force of gravity, terminal velocity is reached Terminal velocity is the highest velocity that an object will reach as it falls
First Law: An object at rest stays at rest or an object in motion, stays in motion (in the same direction/at the same speed) unless acted upon by an unbalanced force Also called the law of inertia
Inertia A property of matter The tendency of an object to resist any change in its motion The greater the mass the greater the inertia The greater the speed the greater the inertia
Examples of Newton’s 1 st Law • a) car suddenly stops and you strain against the seat belt • b) when riding a horse, the horse suddenly stops and you fly over its head • c) the magician pulls the tablecloth out from under a table full of dishes • d) the difficulty of pushing a dead car • e) lawn bowling on a cut and rolled lawn verses an uncut lawn • f) car turns left and you appear to slide to the right
Examples of Newton’s 1 st Law
Second law: The greater the force applied to an object, the more the object will accelerate. It takes more force to accelerate an object with a lot of mass than to accelerate something with very little mass. The player in black had more acceleration thus he hit with a greater amount of force
Second law: The greater the force, the greater the acceleration The greater the mass, the greater the force needed for the same acceleration Calculated by: F = ma (F = force, m = mass, a = acceleration)
Examples of Newton’s 2 nd Law a) hitting a baseball, the harder the hit, the faster the ball goes b) accelerating or decelerating a car c) The positioning of football players massive players on the line with lighter (faster to accelerate) players in the backfield d) a loaded versus an unloaded truck
Examples of Newton’s 2 nd Law
Examples of Newton’s 2 nd Law The second law states that unbalanced forces cause objects to accelerate with an acceleration which is directly proportional to the net force and inversely proportional to the mass. This one is telling us that big heavy objects don’t move as fast or as easily as smaller lighter objects. It takes more to slow down a charging bull then to slow down a charging mouse.
third law: For every action force, there is an equal and opposite reaction force. (Forces are always paired)
Examples of Newton’s 3 rd Law a) rockets leaving earth b) guns being fired c) two cars hit head on d) astronauts in space e) pool or billiards f) jumping out of a boat onto the dock g) sprinklers rotating
Examples of Newton’s 3 rd Newton’s third law: "For every there is an equal and Lawaction, opposite reaction. " When you fire a gun you feel the recoil. Some of the funniest things in cartoons follow physics that have been exaggerated or just plain ignored. Wyle Coyote hangs suspended in space over that canyon for a lot longer than an object would in reality, but it is the anticipation of the drop and Wyle's facial recognition of the upcoming pain that is so classically cartooney. So some laws are stretched for comical effect.
Examples of Newton’s 3 rd Law
Momentum: The quantity of motion A property of moving objects Calculated by: P = mv (p = momentum, m = mass, v = velocity) Law of conservation of momentum: momentum the total amount of momentum of a group of objects does not change unless outside forces act on the objects Rollercoaster Momentum