Unit 12 Notes

Motion & Forces

Amusement Park Forces

FORCE = Any push or pull which causes something to move or change its speed or direction

What is a Force?

Can you think of examples of forces?

Visible Forces?

Invisible Forces?

What is a Force?

Forces can be BALANCED or UNBALANCED

Balanced forces are equal in size and opposite in direction Cancel out Unbalanced forces do not cancel out Can be in the same direction (add) or opposite direction (subtract) Result in a NET Force Amusement Park ForcesUnit for ForceMeasured in Newtons (N) Weight is the measure of the force of gravityEx: Net Force = 30N

Net Force = 35N40N10N25N10N

Explain the forces A force of attraction between all object.

Depends upon the mass of the objects and the distance between the objects

GRAVITYGalileo Galilei

An English physicist who discovered that gravity pulls all objects toward Earth at the same speed (by shooting cannonballs)

Issac Newton English Scientist that was able to extend the idea of gravity to all objects in the universe. Universal Law of GravityAll object in the universe exert a gravitational force on each other

The greater the mass, the greater the forceThe greater the distance, the less the forceAcceleration due to gravity = 9.8 m/s2

What is Gravity?Gravity in Space

Air resistance: The force of air exerted on a falling object

The air pushes up as gravity pulls downDependent upon the shape and surface area of the object

Terminal VelocityWhen the air resistance equals the force of gravity

Terminal velocity is the highest velocity that an object will reach as it falls

What is Motion?Motion: A change in position of an object compared to a reference point

Motion involves all of the following:

What is Motion?SpeedThe rate of change in positionSpeed = distance time or

= distance time

What is Motion?VelocitySpeed plus directionExample: 50 km/hour north

What is Motion?AccelerationThe rate of change in velocityPositive acceleration = speeding upNegative acceleration = slowing down (decelerate) or change in direction!!Acceleration = (Final Velocity Initial Velocity) Time

What is Friction?Friction = A force that opposes or slows down motionDepends upon the type of surfaces and the force pressing the surfaces togetherChanges motion into heat

What is Friction?What are some ways athletes uses friction?

Newton's Laws of Motion

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 forceAlso called the law of inertia

Newton's Laws of MotionInertiaA property of matterThe tendency of an object to resist any change in its motionThe greater the mass the greater the inertiaThe greater the speed the greater the inertia

Examples of Newtons 1st Lawa) 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 Newtons 1st 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.

Newton's Laws of Motion

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 accelerationThe greater the mass, the greater the force needed for the same accelerationCalculated by: F = ma(F = force, m = mass, a = acceleration)

Newton's Laws of MotionExamples of Newtons 2nd Lawa) 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 Newtons 2nd LawExamples of Newtons 2nd 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 dont 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)Newton's Laws of Motion

Examples of Newtons 3rd Lawrockets leaving earthguns being firedc) 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 Newtons 3rd Law

Newtons third law: "For every action, there is an equal and 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 Newtons 3rd Law

Momentum: The quantity of motionA property of moving objectsCalculated by: P = mv (p = momentum, m = mass, v = velocity)Law of conservation of momentum: the total amount of momentum of a group of objects does not change unless outside forces act on the objects

Rollercoaster Momentum