Answer:
The focal length of a lens is refers to the distance from the center of the lens to the principal foci.
I believe your answer is d).
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Answer:
i) 2
ii) No
Explanation:
i) The man will hear two sounds: one through the rail, and one in the air.
ii) The sounds will not reach the man at the same time. Sound travels faster through solids than through gases, so he will hear the sound through the rail before he hears the sound in the air.
Answer:
the earthquake's epicenter is L = 1091.2 km away
Explanation:
if the P and S waves start from the same place (x=0) :
P would travel the distance L in , L = vP * tP
P would travel the distance L in , L = vS * tS
therefore
vP * tP= vS * tS
if the difference in time d= tS-tP → tS=d+tP , then
vS * tS= vP * tP
vS *(d+tP) = vP * tP
vS*d + vS*tP = vP * tP
vS*d = vP * tP - vS*tP = (vP - vS) * tP
tP = vS*d / (vP - vS)
replacing values
tP = vS*d / (vS - vP) = 5.1 km/s * 1.5 min*60 s/min / ( 8.8 km/s - 5.1 Km/s) = 124 s
therefore
L = vP*tP = 8.8 km/s * 124 s = 1091.2 km
W=F*s
W=9000*0
W=0
W:Work
F:Force
s:Distance