Since the floor is rough, it exerts both a normal force N1 and a frictional force f1 on the ladder. However, since the wall is frictionless, it exerts only a normal force N2 on the ladder. The ladder has a length of
L = 4.50 m,
a weight of
WL = 51.5 N,
and rests against the wall a distance
d = 3.75 m
above the floor. If a person with a mass of
m = 90 kg
is standing on the ladder, determine the following.
(a) the forces exerted on the ladder when the person is halfway up the ladder (Enter the magnitude only.)
N1 = N
N2 = N
f1 = N
(b) the forces exerted on the ladder when the person is three-fourths of the way up the ladder (Enter the magnitude only.)
N1 = N
N2 = N
f1 = N

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.