SOLUTION: The force due to gravity on a man is proportional to his mass and inversely proportional to the square of his distance from the centre of the Earth. If a man weighs 90kg and the ra

Algebra ->  Equations -> SOLUTION: The force due to gravity on a man is proportional to his mass and inversely proportional to the square of his distance from the centre of the Earth. If a man weighs 90kg and the ra      Log On


   

Question 1119344: The force due to gravity on a man is proportional to his mass and inversely proportional to the square of his distance from the centre of the Earth. If a man weighs 90kg and the radius of the Earth is 6.4 x 10^6 metres, the force acting on him is 8 x 10^-4 Newton. Find the force acting on a man weighing 80kg when he is in a satellite 1 million metres above the surface of the Earth
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
The force due to gravity on a man is proportional to his mass and inversely proportional to the square of his distance from the centre of the Earth. If a man weighs 90kg and the radius of the Earth is 6.4*10^6 metres, the force acting on him is 8*10^-4 Newton. Find the force acting on a man weighing 80kg when he is in a satellite 1 million metres above the surface of the Earth
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Don't use x for multiply, use * (Shift 8)
1 million meters = 1000 km.
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The force due to gravity on a man is proportional to his mass and inversely proportional to the square of his distance from the centre of the Earth. If a man weighs 90 kg and the radius of the Earth is 6400 km, the force acting on him is 8*10^-4 Newton. Find the force acting on a man weighing 80kg when he is in a satellite 1000 km above the surface of the Earth
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1000 km above the surface --> 7400 km from the CG.
F = k*m/d^2 --- k = constant
8e-4 = k*90/6400^2
Solve for k, ignore units
k = 8e-4*6.4^2e4/90 = 8*40.96/90 = 163.84/45
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It's not necessary to solve for k, use proportions:
F%5B1%5D%2A%28r%5B1%5D%29%5E2+=+F%5B2%5D%2A%28r%5B2%5D%29%5E2

F%5B2%5D+=+8e-4%2A%286400%2A%2880%2F90%29%2F7400%29%5E2
F2 =~ 5.319e-4 Newtons
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Your input data is suspect, but that is how you do it.
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Note 1*10-4 = 1e-4
Saves a lot of typing, and is commonly used in computer programming.

Answer by ikleyn(52800) About Me  (Show Source):
You can put this solution on YOUR website!
.
The force due to gravity on a man is proportional to his mass and inversely proportional to the square of his distance
from the centre of the Earth. If a man weighs 90kg and the radius of the Earth is 6.4 x 10^6 metres, the force acting on him
is 8 x 10^-4 Newton. Find the force acting on a man weighing 80kg when he is in a satellite 1 million metres above the surface of the Earth
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The weight of the mass of  90 kg  at the Earth surface  IS  NOT  8 x 10^(-4) Newton.


At the Earth surface,  the mass of  90 kg  weights about  9*10^2 newtons


            (Weight = mass * 9.81 m/s^2,   or,  approximately,   90*10 = 9*10^2 newtons).


Your input is  FATALLY  INCORRECT  and shows that your knowledge of Physics is about zero.


I really don't know what to discuss with the person who does not know basics (and posts incorrect assignments).


I only can advise him to take a Physics textbook and to read the chapter "Forces".