Unit 12 Notes

Motion & Forces

Amusement Park ForcesFORCE = 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 directionUnbalanced 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?Can you think of examples of forces?

Balanced Forces?

Unbalanced Forces?

What is a Force?

GRAVITY: An attraction force between all massesNewtons universal law of gravitation: Every object in the universe exerts a gravitational attraction to all other objects in the universeThe 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 forceThe greater the distance, the less the forceAcceleration due to gravity = 9.8 m/s/s or 9.8 m/s2

What is Gravity?Gravity in SpaceWeight is a measure of the gravitational force between two objectsThe greater the mass the greater the force (weight)Measured in units called Newtons (N)Weightlessness free from the effects of gravity

Gravity by Brainpop) How does the gravity on the moon compare to the gravity on Earth?

) Why dont you notice your own gravitational pull on the Earth?

) On what two things does the force of gravity depend?

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 objectWhen the air resistance equals the force of gravity, terminal velocity is reachedTerminal 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)

Acceleration = Vfinal Vinitial Time or = Velocity TimeWhat is Friction?Friction = A force that opposes or slows down motionCaused by the physical contact between moving surfacesThe amount of friction depends upon the kinds of surfaces and the force pressing the surfaces togetherChanges motion into heat

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

Acceleration by Brainpop

) What units are used to measure speed?

) What units are used to measure acceleration?

) What is another way to say slowing down in terms of acceleration?

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 MomentumNewtons Laws by Brainpop) Why does a ball roll across a rug and come to a stop?

) What is a net force?

) Give an example of Newtons 3rd Law:

Force by Brainpop) What famous physicist are units of force named after?

) What does velocity measure?

) If Moby has a mass of 50 kg and Tim has a mass of 40 kg, who would require more force to move?