Momentum. Momentum. Impulse. Impulse Momentum Theorem. Deriving Impulse. v a t. Momentum and Impulse. Impulse. v t

Transcription

1 Moentu and Iule Moentu Moentu i what Newton called the quantity of otion of an object. lo called Ma in otion The unit for oentu are: = oentu = a = elocity kg Moentu Moentu i affected by a and elocity eeding bullet ay hae the ae oentu a a low oing car The ore oentu an object ha, the ore force will be needed to change it otion Exale: It i hard to to a large, fat train What i the oentu of a 00 kg car driing at 6 /? = 00 kg = 6 / Iule Iule i the change in oentu Iule relate the tie and force needed to change an object oentu ( 00kg)(6 ) kg More contact e Le force needed Le contact e Le force needed 3 4 Iule Moentu Theore I = iule, but oetie J i ued. Iule t f i We know: Deriing Iule a a t Then ubtitute and rearrange The unit for iule are: N or kg a t t 1

2 Moentu and Iule Iule Exale What hould a boxer do when he get hit? t When a boxer roll with the unch he increae the contact tie of the unch. Thi ake the force uch aller. More Iule Exale Droing an egg on a illow will increae the tie of the oentu change. Thi lower the force. car ue an airbag to increae the tie the head change it oentu during an accident. car driing into a wall will change it oentu ery fat, reulting in a huge force. car hitting the brake and lowing down gradually will reult in ery low force. 7 8 Iule Moentu Theore I t f ) ( i I = iule = change oentu = force = a t = tie f = final elocity i = initial elocity What force doe it take to to a 00 kg car driing at 6 /? Cae 1 Ue brake for 1 econd Cae Crah into a wall Sto in 0. t ( f ) ( i 00kg (0 6 ) Coon unit for iule are: N kg What force doe it take to to a 00 kg car driing at 6 /? t t Cae 1 Ue brake for 1 econd 57000kg 700 N 1 What force doe it take to to a 00 kg car driing at 6 /? Cae Crah into a wall Sto in kg N 0. It i tyically afer to ue brake to to a car intead of uing wall. 11 1

3 Moentu and Iule Coneration of Moentu Total oentu in a yte doe not change. Moentu i tranferred between object Exale Equation (deend on ituation) i i i i f f f f Coneration of Moentu Each roble ut be analyzed to figure out what i going on. Do object: bounce away in ooite direction? Stick together? (Car crah) Searate? (ullet giing recoil) Tranfer oentu? (Pool ball) Chooe an aroriate coordinate yte to decribe the elocity of each object (+/ ) n atronaut at ret in ace fire a thruter itol that exel 35 g of hot ga at 875 /. The cobined a of the atronaut and itol i 84 kg. How fat and in what direction i the atronaut oing after firing the itol? kg 84 kg i 0 i 0 f 875 Object earate in ooite direction Deelo equation to ue i The initial ter dro out ince i = 0 / 0 f f f f f f Sole for f Plug and Chug f f Elatic Colliion Thi occur when car bounce off each other. The ditance the car bounce deend on the original oentu 0.035kg 875 f kg Negatie elocity ean ooite direction 17 i i i i f f f f 18 3

4 Moentu and Iule Inelatic Colliion Thi occur when car tick together. The car will cobine and oe in the direction of the car with greater oentu i i i i f ( ) f 1875 kg car going 3 / rear end a 105 kg coact car going 17 / on ice in the ae direction. The two car tick together. How fat do the two car oe together iediately after the colliion? 1875kg 105kg i 3 i Object cobine, continue in ae direction Deelo equation to ue i i i i f ( ) Sole for f f i i f Plug and Chug i 1875kg kg 105kg kg i / 4315kg 1745kg f 1875kg 105kg f Moentu in Two Dienion Each oentu (or elocity) ut be broken to x and y coonent (in, co, etc) Su coonent oenta (elocitie) and find the reultant oentu (elocity) Reeber to ue = for each oentu. Ue whicheer for, or, that i ore ueful. 3 Moentu in Two Dienion Exale object, and, crahing into each other fro different direction i,x + i,x = P f,x i,y + i,y = P f,y Reultant Moentu ngle fro x axi f tan f, x f 1 P P f f, x 4 4

5 Moentu and Iule 135 kg car,, oing north at 7.0 /, collide with a 165 kg car,, oing eat at 11.0 /. The two car are tuck together. In what direction and with what eed do they oe after the colliion? 135kg 165kg i 7 i 11 ind total oentu for each coonent i, x i, x f, x 135kg kg i i, y f 165kg kg f ind reultant oentu f f, x f 3815kg 35775kg f kg Relate oentu to elocity f f 7 Sole for f f f inding Direction kg 135kg 165kg f 1.3 f 35775kg tan 1 N of E kg / 8 5