Piv txwv ntawm cov nthwv dej ruaj khov thiab cov nthwv dej sawv ntsug

4 Piv txwv ntawm cov nthwv dej ruaj khov thiab cov nthwv dej sawv ntsug

1. Ib txoj hlua ntev 0,6 meters. Yog tias qhov nro ntawm txoj hlua raug kho kom qhov ceev ntawm nthwv dej yog 120 m/s, ces qhov zaus tseem ceeb yog...
A. 100 Hz
B. 120 Hz
C. 140 Hz
D. 150 Hz
E. 350 Hz
Kev Sib Tham:

Nws yog paub :
Ntev ntawm cov hlau (L) = 0,6 meters
Qhov ceev ntawm nthwv dej (v) = 120 m/s.
Nug :
zaus tseem ceeb (f₁)?
Jawb :
Tus qauv zaus tseem ceeb (f)₁) nthwv dej ruaj khov lossis nthwv dej sawv ntsug uas ob qho kawg ntawm txoj hlua txuas nrog:
f₁ = v / 2L
zaus tseem ceeb (f₁) nthwv dej yog:
f₁ = 120 / (2)(0,6) = 120 / 1,2 = 100 hz
Cov lus teb yog lawm yog A.

2. Vim yog qhov kev cuam tshuam, ib nthwv dej ruaj khov tau tsim nrog cov qauv: y = 0,4 sin (0,6 π x) cos π (8t) meters. Los ntawm cov qauv saum toj no, qhov ceev ntawm nthwv dej cuam tshuam yog...
A. 10,0 m/s
B. 11,5 m/s
C. 12,4 m/s
D. 13,2 m/s
E. 14,0 m/s
Kev Sib Tham:
Nws yog paub :
Nug :
Qhov ceev ntawm nthwv dej uas cuam tshuam (v)?
Jawb :

Cov lus teb yog D.

3. Ib txoj hlua ntev 3 m raug khi rau ntawm ib kawg thiab lwm qhov kawg txuas nrog lub vibrator. Thaum lub vibrator raug co, ib lub nthwv dej ruaj khov raug tsim rau ntawm txoj hlua raws li pom hauv daim duab:

Qhov chaw ntawm lub plab thib 5 ntawm qhov kawg khi yog ...

A. 0,9 m

B. 1,2 m

C. 2,5 m

D. 2,7 m

E. 3,0 m

Kev Sib Tham

Qhov kawg ntawm txoj hlua txuas nrog lub vibrator tuaj yeem txav mus los tau yooj yim thaum qhov kawg ntawm txoj hlua txuas nrog tus ncej raug khi.

Qhov nrug ntawm ob lub nodes ze tshaj plaws = 3 meters / 5 = 3/5 meters.

Qhov chaw ntawm thawj lub pob caus ntawm qhov kawg khi = 3/5 meters

Qhov chaw ntawm lub pob caus thib 2 ntawm qhov kawg khi = 2 (3/5 meter) = 6/5 meters

Qhov chaw ntawm lub pob caus thib 3 ntawm qhov kawg khi = 3 (3/5 meter) = 9/5 meters

Qhov chaw ntawm lub pob caus thib 4 ntawm qhov kawg khi = 4 (3/5 meter) = 12/5 meters

Qhov nrug ntawm ib lub node thiab lub plab ze tshaj plaws = 1/2 (3/5 meter) = 3/10 meter.

Qhov chaw ntawm lub plab thib 5 ntawm qhov kawg khi = qhov deb ntawm lub pob caus thib 4 ntawm qhov kawg khi + Qhov deb ntawm ib lub pob caus thiab lub plab ze tshaj plaws = 12/5 + 3/10 = 24/10 + 3/10 = 27/10 = 2,7 meters.

Cov lus teb yog D.

4. Hauv Melde qhov kev sim, ib nthwv dej ruaj khov tau txais raws li qhia hauv daim duab. Yog tias qhov ntev ntawm txoj hlua siv yog 1,5 m, ces qhov chaw ntawm lub node thib plaub suav los ntawm qhov chaw co yog...

A. 0,40 m

B. 0,54 m

C. 0,96 m

D. 1,02 m

E. 1,10 m

Kev Sib Tham

Qhov nrug ntawm ob lub nodes ze tshaj plaws = 1,5 meters / 11 = 1,5/11 meters.

Qhov chaw ntawm node 1 ntawm qhov chaw co = 1,5/11 meters

Qhov chaw ntawm qhov thib 2 ntawm qhov chaw co = 2 (1,5/11 meters) = 3/11 meters

Qhov chaw ntawm qhov thib 3 ntawm qhov chaw co = 3 (1,5/11 meters) = 4,5/11 meters

Qhov chaw ntawm qhov chaw thib 4 ntawm qhov chaw co = 4 (1,5/11 meters) = 6/11 meters = 0,54 meters

Cov lus teb yog B.