Answer:
To describe motion accurately and completely, a frame of reference is necessary. frame of reference ( or reference frame) consists of an abstract coordinate system and the set of physical reference points that uniquely fix ( locate and orient ) the coordinate system and standardize measurements within that frame.
Explanation:
The different observations occur because the two observers are in different frames of reference. A frame of reference is a set of coordinates that can be used to determine positions and velocities of objects in that frame; different frames of reference move relative to one another.
Answer:
v = 19.6 m/s
Explanation:
Height of building = 30.6 m.
Height of window from the ground level= 10.7 m.
Acceleration due to gravity = 9.8 
At initial condition ball at rest condition so u= 0 m/s.
Lets take when passes through the window ,velocity is v.
Here acceleration is constant so we can apply motion equation .
We know that
v= u + a t
So by putting the values
v = 0 +9.8 x 2
v = 19.6 m/s
So the velocity of ball is 19.6 m/s when passes through the window after 2 s.
The electrostatic force is directly proportional to the product of the charges, by Coulomb's law.
F α Qq
If the charges are now half the initial charges:
<span>F α (1/2)Q *(1/2)q
</span>
F α (1/4)Q<span>q
The new force when the charges are each halved is (1/4) the first initial force experienced at full charge.</span>
La lumière qui vient des étoiles.
Because earths gravitational force is greater than that of the moon.
