I'm pretty sure it's sunscreen
Answer: 6,400 km
Explanation:
The weight of a person is given by:

where m is the mass of the person and g is the acceleration due to gravity. While the mass does not depend on the height above the surface, the value of g does, following the formula:

where
G is the gravitational constant
M is the Earth's mass
r is the distance of the person from the Earth's center
The problem says that the person weighs 800 N at the Earth's surface, so when r=R (Earth's radius):
(1)
Now we want to find the height h above the surface at which the weight of the man is 200 N:
(2)
If we divide eq.(1) by eq.(2), we get


By solving the equation, we find:

which has two solutions:
--> negative solution, we can ignore it
--> this is our solution
Since the Earth's radius is
, the person should be at
above Earth's surface.
Answer:

Explanation:
distance between ship A and B = 32 mile
Ship A velocity in south, dx/dt = -16 mph
Ship B is sailing toward east with speed, dy/st = 12 mph
time = 1 hour
rate of change of distance between them = ?
x be the distance travel after t time
X = 32 + x
Let distance between them be z
now, using Pythagoras theorem to calculate distance between ships after 1 hours
z² = x² + y²
z² = (32 + x)² + 12²
z² = (32 - 16)² + 12²
z = √400
z = 20 miles
now, calculation of rate of change of distnace
z² = (32 + x)² + y²
differentiating both side w.r.t. time





hence, the rate is the distance between them changing at the end of 1 hour is equal to 