the force that attract any object to another =gravity
Given that,
For glasses:
distance, s = 42 m
a= -g = -9.81 m/s²
we can calculate time taken by glasses to hit the ground as follow:
s= Vi* t + 1/2 at²
Since at top initial velocity, Vi= 0
42 = 0 - 0.5* 9.81 t²
t = 2.926 s
Pen is drop 2 second after the glasses is dropped. So time difference will be:
Δt = 2.926 - 2 = 0.926 s
Distance covered by Pen in 0.926 s can be calculated as:
s = 0 - 0.5* 9.81 * 0.926²
s= 4.2 m
Distance of pen from ground will be, 42-4.2 = 37.8 m
When the glasses hit the ground, the pen will be 37.8 m above the ground.
Answer: option (D.)They send signals in the gigahertz range to relays in the line of sight.
Explanation:
Microwaves are a form of electromagnetic waves with wavelengths between from about a meter to a millimeter; and they possess frequencies between 300 mega hertz(MHz )and 300 giga hertz(GHz.)
Microwaves travel by line-of-sight; unlike other radio waves of lower frequency. They do not bend around hills, nor follow the earth's surface as ground waves, nor reflect from the ionosphere .Therefore land microwave communication links are restricted only tovisual horizon to about 40 miles (64 km).
This is because of Convection. Convection is the transfer of thermal energy by the movement of particles from one part of something to another.