A > Is the correct answer :)
Answer:9.75 m/s
Explanation:
Given
Length of ladder 
Foot the ladder is moving away with speed of 
From diagram
------1
at 
Now differentiating equation 1 w.r.t time
negative indicates distance is decreasing with time
Answer: 0 km/h
Explanation:
As a vector, the plane's velocity is 100 km/h (west) - 100 km/h (east) = 0 km/m.
To an observer on the ground, the plane will be standing still.
Copernicus's model states that the sun is in the center, and that the planets move around it in a circle. Kepler's first law of planetary motion says that they move around the sun in an ellipse.
Answer:
The second vector 
points due West with a magnitude of 600N
Explanation:
The original vector 
points with a magnitude of 200N due east, the Resultant vector 
points due west (that's how east/west direction can be interpreted, from east to west) with a magnitude of 400N. If we choose East as the positive direction and West as the negative one, we can write the following vectorial equation:
With the negative sign signifying that the vector points west.
