Motion,Momentum,& Centripetal Force

Newton’s Laws of Motion 1 st Law: An object in motion remains in motion & an object at rest remains at rest unless acted upon by an outside force.1 st Law: An object in motion remains in motion & an object at rest remains at rest unless acted upon by an outside force. Inertia: The tendency of an object to resist any change in its motionInertia: The tendency of an object to resist any change in its motion Newton's 1st Law of Motion in a car crash video clip Newton's 1st Law of Motion in a car crash video clip

Car Crashes & Newton’s 1 st Law of Motion 3 collisions occur in a car crash:3 collisions occur in a car crash: 1.The car crashes & stops (occurs within 1/10 of a second) 2.The occupant stops (same speed the car was going) 3.The occupants internal organs stop (same speed as car) 4 ways seat belts help save lives:4 ways seat belts help save lives: 1.Keep occupants in the vehicle (not thrown out into traffic/etc.) 2.Keep occupants from hitting hard parts of the vehicle 3.Spread the force over a larger area (reduces pressure) 4.Increases the stop time (seatbelt gives a little)

Newton’s Laws of Motion 2 nd 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/s 2, it needs _20N_ force to do this. 10kg x 2m/s 2 = 20N

Mass: The total amount of matter in a substanceMass: The total amount of matter in a substance As mass increases, inertia increases, and the force needed for acceleration increases.As mass increases, inertia increases, and the force needed for acceleration increases.

Newton’s 3 rd Law of Motion: For every action, there is an equal and opposite reaction. (equal in force, opposite in direction).

Momentum: The product of an object’s mass and velocity. p=mv or mv = p (p=momentum, m = mass, v = velocity)Momentum: The product of an object’s mass and velocity. p=mv or mv = p (p=momentum, m = mass, v = velocity) Ex. 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 Impulse: m x v ÷ stop timeImpulse: m x v ÷ stop time Ex: a 100 lb person traveling at 50 mph in a car crash hits the dash board in 1/10 second. 100 lb x 50 mph ÷ 0.1 sec = 50,000 lb impulse momentum and impulse video clip momentum and impulse video clip

Law of Conservation of Momentum:Law of Conservation of Momentum: the total momentum of any group of objects remains the total momentum of any group of objects remains the same unless outside forces act on the objects. Law of Conservation of MomentumLaw of Conservation of Momentum Pi = Pf Pi = Pf M1V1 + M2V2 = MTVf (40 kg ∙ 10 m/s) + (30 kg ∙ 5 m/s) M1V1 + M2V2 = MTVf (40 kg ∙ 10 m/s) + (30 kg ∙ 5 m/s) (400 kg∙m/s) + (150 kg∙m/s) = 70 kg ∙ Vf (400 kg∙m/s) + (150 kg∙m/s) = 70 kg ∙ Vf Pi ÷ MT =Vf 550 ÷ 70 = 7.68 m/s Pi ÷ MT =Vf 550 ÷ 70 = 7.68 m/s

Centripetal Force: A force that causes objects to move in a circle (center-seeking)Centripetal Force: A force that causes objects to move in a circle (center-seeking) Centrifugal force = center-fleeingCentrifugal force = center-fleeing centripetal force video clip centripetal force video clip spinning video clip spinning video clip