To find the ratio of planetary speeds Va/Vb we need the orbital velocity formula:
V=√({G*M}/R), where G is the gravitational constant, M is the mass of the distant star and R is the distance of the planet from the star it is orbiting.
So Va/Vb=[√( {G*M}/Ra) ] / [√( {G*M}/Rb) ], in our case Ra = 7.8*Rb
Va/Vb=[ √( {G*M}/{7.8*Rb} ) ] / [√( {G*M}/Rb )], we put everything under one square root by the rule: (√a) / (√b) = √(a/b)
Va/Vb=√ [ { (G*M)/(7.8*Rb) } / { (G*M)/(Rb) } ], when we cancel out G, M and Rb we get:
Va/Vb=√(1/7.8)/(1/1)=√(1/7.8)=0.358 so the ratio of Va/Vb = 0.358.
Answer:
D.300nm
Explanation:
Wavelength = Speed of light / Frequency of light.....
where the speed of light is...(3 × 10^8)
Wavelength = (3 × 10^8)/(1 × 10^15)
Wavelength = 3 × 10^-7
;Wavelength = 300 × 10^-9
Hence its....300 nm
Answer:
The work done by gravity is 
Explanation:
The data given in the question is :
Mass is 
Height from ground is 
As we know , the work done is state function , it depends on initial and final position not on the path followed.
So, work done by gravity = change in potential energy
Work done = Initial potential energy - final potential energy
Insert values from question
Work done = 
Work done = 
So, work done = 
Hence the work done by gravity is 