Answer:
A) a frictional force is acting on it
Explanation:
The crate is sliding down the inclined ramp at constant velocity: constant velocity means zero acceleration, a = 0. According to Newton's second law:
F = ma
this also means that the net force acting along the direction of the slope is zero.
Without frictional force, there would be only one force acting along this direction: the component of the weight of the crane parallel to the slope, acting downward:

where
is the angle of the incline. Therefore, the net force along this direction would not be zero. In order to have a net force of zero, there must be another force acting upward on the crate: and the only force that is possibly acting on the crate against its direction of motion is the frictional force, whose magnitude must be equal to
, in order to produce a net force of zero (and therefore, a zero acceleration).
Solids wall cement chat door tree
liquids oil ,water ,saline solution,soap
gases. tear gas meathian gas steam
It should be at the very top since it has more space to fall which gives it more potential energy
The orbital radius is: 
Explanation:
The problem is asking to find the radius of the orbit of a satellite around a planet, given the orbital speed of the satellite.
For a satellite in orbit around a planet, the gravitational force provides the required centripetal force to keep it in circular motion, therefore we can write:

where
G is the gravitational constant
M is the mass of the planet
m is the mass of the satellite
r is the radius of the orbit
v is the speed of the satellite
Re-arranging the equation, we find:

Learn more about circular motion:
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