Motion, Motion,

Momentum, Momentum,

& &

Centripetal ForceCentripetal Force

Newton’s Laws of Motion• 11st st Law: An object in motion remains in Law: An object in motion remains in

motionmotion & an object at rest remains at & an object at rest remains at restrest unless acted upon by an unless acted upon by an outside outside force.force.

• InertiaInertia: The tendency of an object to resist : The tendency of an object to resist any change in its motionany change in its motion

Newton's 1st Law of Motion in a car crash video clipNewton's 1st Law of Motion in a car crash video clip

Car Crashes & Newton’s 1Car Crashes & Newton’s 1stst Law of Law of MotionMotion• 3 collisions occur in a car crash:3 collisions occur in a car crash:

1.1. The The carcar crashes & stops crashes & stops (occurs within (occurs within 1/101/10 of a second)of a second)

2.2. The The occupantoccupant stops stops (same speed the car was going)(same speed the car was going)

3.3. The occupants The occupants internal organsinternal organs stop stop (same speed as car)(same speed as car)

• 4 ways seat belts help save lives:4 ways seat belts help save lives:

1.1. Keep occupants in the vehicle Keep occupants in the vehicle (not thrown out into traffic/etc.)(not thrown out into traffic/etc.)

2.2. Keep occupants from hitting hard parts of the vehicleKeep occupants from hitting hard parts of the vehicle

3.3. Spread the force over a larger area Spread the force over a larger area (reduces pressure)(reduces pressure)

4.4. Increases the stop time Increases the stop time (seatbelt gives a little)(seatbelt gives a little)

Newton’s Laws of MotionNewton’s Laws of Motion• 2nd Law: The force of an object is equal to the product of its

mass and acceleration.

F = m x a (m = F/a or a = F/m) (F = force, m = mass, a = acceleration)

(Unit of measure for force is the Newton N)

• Ex: an object has a mass of 10kg and accelerates at 2m/s2, it needs _20N_ force to do this. 10kg x 2m/s2 = 20N

• MassMass: The total amount of matter in a substance: The total amount of matter in a substance

• As mass increases, inertia As mass increases, inertia increasesincreases, and the force , and the force needed for acceleration needed for acceleration increases.increases.

Newton’s 3rd Law of Motion: For every action, there is an equal and opposite

reaction. (equal in force, opposite in direction).

Bill Nye: Motion vidBill Nye: Motion videoeoNewton’s Laws-7:55Newton’s Laws-7:55

• MomentumMomentum: The product of an object’s mass and velocity. : The product of an object’s mass and velocity. p=mv or mv = p p=mv or mv = p (p=momentum, m = mass, v = velocity)(p=momentum, m = mass, v = velocity)

Ex. a 0.5 kg ball thrown at 6 m/sEx. a 0.5 kg ball thrown at 6 m/s 0.5 kg x 6 m/s = 3 kg · m/s 0.5 kg x 6 m/s = 3 kg · m/s

• ImpulseImpulse: m x v ÷ stop time: m x v ÷ stop timeEx: a 100 lb person traveling at 50 mph Ex: a 100 lb person traveling at 50 mph in a car crash hits the dash board in 1/10 second.in a car crash hits the dash board in 1/10 second.100 lb x 50 mph ÷ 0.1 sec = 50,000 lb impulse100 lb x 50 mph ÷ 0.1 sec = 50,000 lb impulsemomentum and impulse video clipmomentum and impulse video clip

• Law of Conservation of Momentum: Law of Conservation of Momentum: the total the total momentummomentum of any group of objects remains of any group of objects remains

the same unless the same unless outsideoutside forces act on the objects. forces act on the objects.

• Law of Conservation of Momentum Law of Conservation of Momentum Pi = Pf Pi = Pf M1V1 + M2V2 = MTVf M1V1 + M2V2 = MTVf (40 kg ∙ 10 m/s) + (30 kg ∙ 5 m/s)(40 kg ∙ 10 m/s) + (30 kg ∙ 5 m/s) (400 kg∙m/s) + (150 kg∙m/s) = (400 kg∙m/s) + (150 kg∙m/s) =

70 kg ∙ Vf70 kg ∙ Vf Pi ÷ MT =Vf 550 ÷ 70 = 7.68 m/s Pi ÷ MT =Vf 550 ÷ 70 = 7.68 m/s

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Bill Nye: Momentum2:20-ruler/coins

10:47-basketball/tennis ball12:10-bowling ball

• Centripetal Force: A force that causes objects to Centripetal Force: A force that causes objects to move in a move in a circlecircle (center-seeking) (center-seeking)

• Centrifugal force = center-fleeingCentrifugal force = center-fleeingBill Nye Spinning Things video (angular momentum at 12 minutes)Bill Nye Spinning Things video (angular momentum at 12 minutes)

centripetal force video clip centripetal force video clip

spinning video clipspinning video clip