On the Moon's surface, lunar astronauts placed a corner reflector, off which a laser beam is periodically reflected. The distanc
e to the Moon is calculated from the round-trip time. The Earth's atmosphere slows down light. Assume the distance to the Moon is precisely 3.84 × 10 8 m 3.84×108 m , and Earth's atmosphere (which varies in density with altitude) is equivalent to a layer 25.0 km 25.0 km thick with a constant index of refraction n = 1.000293 n=1.000293 . What is the difference in travel time for light that travels only through space to the moon and back and light that travels through the atmosphere and space? difference in travel time:
1 answer:
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Answer:
40 N
Explanation:
Explanation:
Given data:
d = 30 mm = 0.03 m
L = 1m
S = 70 Mpa
Δd = -0.0001d
Axial force = ?
validity of elastic deformation assumption.
Solution:
O'₂ = Δd/d = (-0.0001d)/d = -0.0001
For copper,
v = 0.326 E = 119×10³ Mpa
O'₁ = O'₂/v = (-0.0001)/0.326 = 306×10⁶
∵δ = F.L/E.A and σ = F/A so,
σ = δ.E/L = O'₁ .E = (306×10⁻⁶).(119×10³) = 36.5 MPa
F = σ . A = (36.5 × 10⁻⁶) . (π/4 × (0.03)²) = 25800 KN
S = 70 MPa > σ = 36.5 MPa
∵ elastic deformation assumption is valid.
so the answer is
F = 25800 K N and S > σ