Answer:
The observer detects light of wavelength is 115 nm.
(b) is correct option
Explanation:
Given that,
Wavelength of source = 500 nm
Velocity = 0.90 c
We need to calculate the wavelength of observer
Using Doppler effect
Where, 
Hence, The observer detects light of wavelength is 115 nm.
Answer:
Below
Explanation:
The cars upward accel adds to the gravity accel (think about how suddenly heavy you feel when the elevator starts to move upward)
F = tension = ma
= 1400 * ( .7 + 9.81) = 14714 N
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