1. Yam khoom qhov hnyav = 2 kg, kev nrawm vim lub ntiajteb txawj nqus = 9.8 m/s 2 , coefficient ntawm kev sib txhuam zoo li qub = 0.2, coefficient ntawm kev sib txhuam kinetic = 0.1. Yam khoom puas nyob twj ywm lossis nrawm? Yog tias yam khoom raug nrawm, nrhiav (a) lub zog net (b) qhov loj thiab kev coj ntawm lub thawv qhov kev nrawm!
tshuaj
Paub:
Qhov hnyav (m) = 2 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 9.8 m/s 2
Tus nqi sib txhuam zoo li qub ( μs ) = 0.2
Coefficient ntawm kinetic sib txhuam ( μk ) = 0.1
Qhov hnyav (w) = mg = (2)(9.8) = 19.6 Newtons
Qhov sib xyaw kab rov tav ntawm qhov hnyav (w x ) = w sin 30 o = (19.6)(0.5) = 9.8 Newtons
Qhov feem ntsug ntawm qhov hnyav (w y ) = w cos 30 o = (19.6)(0.5√3) = 9.8√3 Newtons
Lub zog ib txwm (N) = w y = 9.8√3 Newtons
Lub zog ntawm kev sib txhuam zoo li qub (f s ) = (0.2)(9.8√3) = 1.96√3 Newton = 3.39 Newton
Lub zog ntawm kev sib txhuam kinetic (f k ) = (0.1)(9.8√3) = 0.98√3 Newton = 1.69 Newton
Tshuaj:
Khoom nyob twj ywm yog tias w x < fs , khoom txav mus rau hauv qab yog tias w x > fs.
w x = 9.8 Newtons thiab f s = 3.39 Newtons.
(a) lub zog tiag tiag
∑ F = w x – f k = 9.8 – 1.69 = 8.11 Newtons
(b) qhov loj thiab kev coj ntawm qhov kev nrawm
∑ F = ma
8.11 = (2) ib
ua = 4.05
Qhov loj ntawm qhov kev nrawm = 4.05 m/s 2 thiab kev coj ntawm qhov kev nrawm = downward.
[irp]
2. Yam khoom hnyav = 4 kg, kev nrawm vim yog lub ntiajteb txawj nqus = 9,8 m/s 2. Coefficient ntawm kev sib txhuam kinetic = 0.2 thiab coefficient ntawm kev sib txhuam static = 0.4. Qhov loj ntawm lub zog F = 40 Newtons. Yam khoom nyob twj ywm lossis swb mus rau hauv qab? Yog tias yam khoom swb mus rau hauv qab, nrhiav (a) lub zog tag nrho (b) qhov loj thiab kev coj ntawm kev nrawm!
tshuaj
Paub:
Qhov hnyav (m) = 4 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 9.8 m/s 2
Tus coefficient ntawm kev sib txhuam zoo li qub ( μs ) = 0.4
Tus coefficient ntawm kinetic friction ( μk ) = 0.2
Qhov hnyav (w) = mg = (4)(9.8) = 39.2 Newtons
Qhov sib xyaw kab rov tav ntawm qhov hnyav (w x ) = w sin 30 o = (39.2)(0.5) = 19.6 Newtons
Qhov feem ntsug ntawm qhov hnyav (wy ) = w cos 30 o = (392)(0..5√3) = 19.6√3 Newtons
Lub zog ib txwm (N) = w y = 19.6√3 Newtons = 33.95 Newtons
lub zog sib txhuam zoo li qub (f s ) = μ s N = (0,4)(33.95) = 13.58 Newtons
Lub zog sib txhuam kinetic (f k ) = μ k N = (0.2)(33.95) = 6.79 Newtons
F = 40 Newtons
Tshuaj:
Tus khoom txav mus rau hauv qab yog tias F < wx + fs . Tus khoom txav mus rau saum toj yog tias F> wx + fs.
F = 40 Newtons, w x = 19.6 Newtons thiab f s = 13.58 Newtons.
F loj dua w x + f s yog li ntawd cov khoom txav mus rau saum.
(a) Lub zog tiag tiag
∑ F = F – w x – f k = 40 – 19.6 – 6.79 = 13.61 Newtons
(b) Qhov loj thiab kev coj ntawm qhov kev nrawm
∑ F = ma
6.4 = (4) ib
ua = 1.6
Qhov loj ntawm qhov kev nrawm yog 1.6 m/s2 thiab qhov kev taw qhia ntawm qhov kev nrawm yog nce mus rau sab saud.
[irp]
[wpdm_package id='481′]
- Qhov hnyav thiab qhov hnyav
- ib txwm muaj zog
- Newton txoj cai thib ob ntawm kev txav mus los
- Lub zog sib txhuam
- Kev txav mus los ntawm qhov chaw kab rov tav yam tsis muaj kev sib txhuam
- Kev txav ntawm ob lub cev nrog tib qhov kev nrawm ntawm qhov chaw ntxhib kab rov tav nrog lub zog sib txhuam
- Kev txav mus los ntawm lub dav hlau inclined tsis muaj lub zog sib txhuam
- Kev txav mus los ntawm lub dav hlau inclined nrog lub zog sib txhuam
- Kev txav mus los hauv lub elevator
- Kev txav ntawm lub cev yog txuas nrog los ntawm cov hlua thiab pulleys
- Ob lub cev uas muaj tib lub zog ntawm kev nrawm
- Kev sib hloov ntawm ib txoj kab tiaj tiaj - dynamics ntawm kev txav mus los ncig
- Kev sib hloov ntawm cov kab nkhaus - dynamics ntawm kev txav mus los ncig
- Kev txav mus los sib xws hauv lub voj voog kab rov tav
- Lub zog centripetal hauv kev txav mus los sib npaug
