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# Lesson_3.3_Printable - Momentum A moving object has a...

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Momentum A moving object has a momentum determined by its mass and velocity. Momentum is the product of mass and velocity Momentum is represented by P and is measured in kg.ms -1 . P = mv kg.ms -1 . Consider a car of mass m oving with a velocity F v o v f Momentum is a vector quantity moving with a velocity v o . It is acted upon by a force F which produces an acceleration a on it. It has a velocity v f after a time t F = ma m(v f – v o ) = P , the change in momentum in the interval t f o v v v a t t - = = ( ) f o m v v t - = 1

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This leads us to conclude that: Force is the rate of change of momentum. Kinetic energy and momentum 0 ( P ) = t F f m v v t = - The kinetic energy K of a moving object can be expressed in terms of its momentum. 2 1 2 K mv = 2 2 2 m v m = 2 2 P m = 2
A 0.5 kg ball is thrown in the x direction with a velocity 10 m.s -1 . It hits a wall and rebounds with the same speed. What is the change in momentum of the ball? he initial momentum of the ball P mv P i = 5 kgms -1 P f = -5 kgms -1 P = -10 kg.mas -1 i m = 0.5 kg, v i = 10 ms -1 i , v f = -10 ms -1 i The initial momentum of the ball P i = mv i The final momentum P f = mv f = 0.5 × (-10 ms -1 i ) The change in momentum P = P f – P i P = - 5 kgms -1 i – (5 kgms -1 ) i = -10 kgms -1 i = 0.5 kg × 10 ms -1 i = 5 kgms -1 i = -5 kgms -1 i 3

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A 0.5 kg ball is thrown against a wall at an angle of 53 o as shown on the right with a velocity of 10 m.s -1 and rebounds with the same speed and at an angle 53 o . Find the change in momentum of the ball. The initial momentum P i = 0.5 kg x 10 ms -1 5 kgms t 53 s shown 4 j P = 4 j 53 o 53 o 127 o P i drawn from the origin makes an angle 53 o and P f makes an angle 127 o . P i in the component form is: P i = 5 cos 53 o i + 5 sin 53 o j The final momentum P f = 5 kgms -1 at 127 o = 5 kgms -1 at 53 o as shown 3 i P f i 53 o = 3 i + 4 j The component form of P f is: P f = 5 cos 127 o i + 5 sin 127 o j = -3 i + 4 j -3 i P = p f – p i = (-3 – (3)) i + (4 – 4) j = -6 i 127 o 4
A loaded dump truck with a total mass of 5.0 × 10 3 kg traveling at 3.0 km.h -1 coasts into a loading dock and collides coming to a stop in 0.64 s. What is the magnitude of the average force exerted on the truck by the dock? The mass of the truck m = 5 × 10

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## This note was uploaded on 05/01/2011 for the course PHY 2048 taught by Professor George during the Fall '10 term at Edison State College.

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Lesson_3.3_Printable - Momentum A moving object has a...

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