Kev txav mus los tsis sib xws - teeb meem thiab kev daws teeb meem
1.
Lub rooj saum toj no qhia cov ntaub ntawv ntawm peb yam khoom uas mus ncig tib qhov deb ntawm qhov kev nrawm tas li.
Qhov ceev kawg ntawm yam khoom P thiab qhov ceev pib ntawm yam khoom Q yog dab tsi?
Tshuaj:
Ua ntej, txiav txim siab qhov deb uas khoom 3 taug kev.
Qhov nrug deb uas khoom 3 tau mus :
Paub :
Qhov ceev pib ( v₂o ) = 0 m/s
Qhov ceev kawg (v t ) = 30 m/s
Kev nrawm (a) = 3 m/s 2
Xav tau : Qhov deb
Tshuaj:
vt2 = vo2 + 2 as
v t 2 – v o 2 = 2 as
30 2 – 0 2 = 2 (3) vib nas this
900 – 0 = 6 vib nas this
900 = 6 vib nas this
s = 900 / 6
s = 150 meters
Qhov ceev kawg ntawm yam khoom 1 :
Paub:
Qhov ceev pib ( v₂o ) = 20 m/s
Kev nrawm (a) = 4 m/s 2
Qhov Nrug Deb (s) = 150 meters
Xav tau: Qhov ceev kawg (v t )
Tshuaj:
vt2 = vo2 + 2 as
v t 2 = 20 2 + 2 (4)(150)
vt2 = 400 + 1200
vt2 = 1600
vt = 40 m/s
Qhov ceev pib ntawm yam khoom 2:
Paub:
Qhov ceev kawg (v t ) = 50 m/s
Kev nrawm (a) = 3 m/s 2
Qhov Nrug Deb (s) = 150 meters
Xav tau: Qhov ceev pib (v o )
Tshuaj:
vt2 = vo2 + 2 as
v t 2 – 2 as = v o 2
50 2 – 2(3)(150) = v2
2500 – 900 = v2
1600 = v2
v₂o = 40 m/s
2. Peb yam khoom taug kev ntawm ib lub dav hlau kab rov tav ntawm qhov nrawm tas li. Peb yam khoom muaj qhov nrawm ib yam. Cov ntaub ntawv ntawm peb yam khoom thaum taug kev hauv 10 vib nas this, qhia hauv daim duab hauv qab no.
Txheeb xyuas P thiab Q.
Tshuaj:
Ua ntej, txiav txim siab qhov kev nrawm ntawm yam khoom 1.
Kev nrawm ntawm yam khoom 1:
Paub:
Qhov ceev pib (v o ) = 2 m/s
Qhov ceev kawg (v t ) = 22 m/s
Qhov Nrug Deb (s) = 120 meters
Xav Tau: Qhov Deb
Tshuaj:
vt2 = vo2 + 2 as
v t 2 – v o 2 = 2 as
22 2 – 2 2 = 2 ib (120)
484 – 4 = 240 ib
480 = 240 ib
ib = 480/240
a = 2 m/s 2
Qhov ceev pib ntawm yam khoom 2 :
Paub:
Kev nrawm (a) = 2 m/s 2
Qhov ceev kawg (v t ) = 24 m/s
Qhov Nrug Deb (s) = 140 meters
Xav tau: Qhov ceev pib (v o )
Tshuaj:
vt2 = vo2 + 2 as
24 2 = vo 2 + 2 (2)(140)
576 = v2 + 560
576 – 560 = v2
16 = v2
v₂o = 4 m/s
Qhov nrug ntawm yam khoom 3:
Paub:
Qhov ceev pib ( v₂o ) = 0 m/s
Qhov ceev kawg (v t ) = 20 m/s
Kev nrawm (a) = 2 m/s 2
Xav tau : Qhov deb (s)
Tshuaj:
vt2 = vo2 + 2 as
20 2 = 0 2 + 2 (2) vib nas this
20 2 = 2 (2) vib nas this
400 = 4 vib nas this
s = 400/4
s = 100 meters s
3. Txheeb xyuas qhov deb uas ib yam khoom taug kev hauv 40 vib nas this.
Tshuaj:
Cheeb Tsam 1 = cheeb tsam ntawm lub duab plaub fab = (20-0)(8-0) = (20)(8) = 160 meters
Cheeb Tsam 2 = cheeb tsam ntawm daim duab peb sab = ½ (25-20)(8-0) = ½ (5)(8) = (5)(4) = 20 meters
Cheeb Tsam 3 = cheeb tsam ntawm daim duab peb sab = ½ (30-25)(8-0) = ½ (5)(8) = (5)(4) = 20 meters
Cheeb Tsam 4 = cheeb tsam ntawm lub duab plaub fab = (40-30)(8-0) = (10)(8) = 80 meters
Qhov deb uas taug kev hauv 40 vib nas this = 160 + 20 + 20 + 80 = 280 meters
4. Qhov kev hloov pauv ntawm qhov ceev ntawm yam khoom hauv 2 vib nas this raws li daim duab hauv qab no. Txheeb xyuas qhov deb uas yam khoom taug kev.
Tshuaj:
Cheeb Tsam 1 = cheeb tsam ntawm daim duab peb sab = ½ (5-0)(20-0) = ½ (5)(20) = (5)(10) = 50 meters
Cheeb Tsam 2 = cheeb tsam ntawm lub duab plaub fab = (15-5)(20-0) = (10)(20) = 200 meters
Cheeb Tsam 3 = cheeb tsam ntawm daim duab peb sab = ½ (20-15)(20-0) = ½ (5)(20) = (5)(10) = 50 meters
Qhov deb uas taug kev hauv 20 vib nas this = 50 + 200 + 50 = 300 meters
- Dab tsi txawv qhov kev txav mus los tsis sib xws ntawm cov kab ncaj thiab cov kev txav mus los sib xws?
- teb: Kev txav mus los uas tsis sib xws yog qhov hloov pauv ntawm qhov ceev raws sijhawm, txhais tau tias muaj kev nrawm nrawm. Qhov sib txawv, kev txav mus los uas sib xws yog qhov uas ib yam khoom txav mus los nrog qhov ceev tas li thiab tsis muaj kev nrawm nrawm.
- Qhov deb uas ib yam khoom taug kev hauv kev txav mus los tsis sib xws muaj feem cuam tshuam li cas rau thaj chaw hauv qab nws daim duab qhia txog lub sijhawm thiab qhov ceev?
- teb: Qhov deb uas ib yam khoom taug kev hauv kev txav tsis sib xws yog sib npaug rau thaj tsam hauv qab nws daim duab qhia ceev-lub sijhawm.
- Yog tias daim duab qhia txog lub sijhawm nrawm ntawm ib yam khoom yog ib txoj kab ncaj nraim saum lub sijhawm, nws qhia txog dab tsi txog kev txav ntawm yam khoom?
- teb: Nws qhia tau tias yam khoom ntawd tab tom khiav nrawm dua tas li. Qhov ceev ntawm yam khoom ntawd yeej nce ntxiv tas li.
- Vim li cas qhov nruab nrab ntawm qhov ceev tsis tuaj yeem suav tau yooj yim ua qhov nruab nrab ntawm qhov pib thiab qhov kawg ntawm qhov ceev hauv kev txav tsis sib xws?
- teb: Rau kev txav tsis sib xws, qhov ceev tsis ruaj khov, yog li qhov kev hloov chaw tiag tiag yuav ntau dua lossis tsawg dua qhov kwv yees los ntawm kev suav nruab nrab ntawm qhov ceev pib thiab qhov ceev kawg. Txoj kev raug rau kev txav tsis sib xws yog kev koom ua ke ntawm qhov ceev hla lub sijhawm muab lossis siv cov qauv kinematic uas suav nrog kev nrawm.
- Koj yuav piav qhia li cas txog kev txav ntawm ib yam khoom uas daim duab qhia txog qhov ceev thiab lub sijhawm yog ib txoj kab ncaj nraim nqes mus rau hauv qab?
- teb: Ib txoj kab ncaj nraim uas nqes mus rau hauv qab ntawm daim duab qhia txog lub sijhawm thiab qhov ceev qhia tias yam khoom ntawd tab tom txav mus nrog qhov kev nrawm tsis zoo tas li, piv txwv li, nws qeeb lossis qeeb yog tias nws muaj qhov ceev zoo thaum xub thawj.
- Hauv kev txav tsis sib xws, qhov ceev tam sim ntawd ntawm ib lub sijhawm tshwj xeeb cuam tshuam li cas rau qhov nqes hav ntawm daim duab qhia lub sijhawm hloov chaw ntawm lub sijhawm ntawd?
- teb: Qhov ceev tam sim ntawd ntawm ib lub sijhawm tshwj xeeb hauv kev txav tsis sib xws yog muab los ntawm qhov nqes hav lossis qhov sib txawv ntawm daim duab qhia lub sijhawm hloov chaw ntawm qhov chaw tshwj xeeb ntawd.
- Ib daim duab nkhaus ntawm daim duab qhia txog qhov xwm txheej ntawm kev txav mus los ntawm ib yam khoom yog dab tsi?
- teb: Ib daim kab nkhaus ntawm daim duab qhia txog kev txav chaw-lub sijhawm qhia txog kev txav tsis sib xws, uas txhais tau tias qhov ceev ntawm cov khoom hloov pauv (txawm tias nce lossis txo qis) dhau sijhawm.
- Yog tias daim duab qhia lub sijhawm hloov chaw ntawm ib yam khoom yog parabolic thiab qhib rau sab saud, koj tuaj yeem xav li cas txog nws qhov kev nrawm?
- teb: Yog tias daim duab qhia lub sijhawm hloov chaw yog ib daim parabola uas qhib rau sab saud, nws qhia tias yam khoom ntawd tab tom dhau qhov kev nrawm nrawm zoo tas li.
- Qhov kev nrawm ntawm ib yam khoom hauv kev txav tsis sib xws muaj feem cuam tshuam li cas rau thaj chaw hauv qab nws daim duab qhia txog qhov ceev thiab lub sijhawm?
- teb: Qhov kev hloov pauv ntawm qhov ceev (uas thaum muab sib npaug rau qhov hnyav muab qhov kev hloov pauv ntawm lub zog) ntawm cov khoom hauv kev txav tsis sib xws yog sib npaug rau thaj chaw hauv qab nws daim duab qhia txog kev nrawm-lub sijhawm. Nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias daim duab qhia txog kev nrawm-lub sijhawm muab qhov kev hloov pauv ntawm qhov ceev, tsis yog qhov kev nrawm ncaj qha.
- Qhov kev nrawm tsis zoo (deceleration) muaj feem cuam tshuam li cas rau qhov ceev ntawm ib yam khoom hauv kev txav tsis sib xws?
- teb: Qhov kev nrawm tsis zoo, feem ntau hu ua kev qeeb, ua rau qhov ceev ntawm yam khoom txo qis. Yog tias yam khoom muaj qhov ceev zoo thaum xub thawj thiab dhau los ua qhov nrawm tsis zoo, nws qhov ceev yuav txo qis, thiab yog tias qhov kev qeeb txuas ntxiv mus, yam khoom tuaj yeem hloov nws txoj kev txav mus los.
