We have the relation

where
denotes the velocity of a body A relative to another body B; here I use B for boat, E for Earth, and R for river.
We're given speeds


Let's assume the river flows South-to-North, so that

and let
be the angle made by the boat relative to East (i.e. -90° corresponds to due South, 0° to due East, and +90° to due North), so that

Then the velocity of the boat relative to the Earth is

The crossing is 153.0 m wide, so that for some time
we have

which is minimized when
so the crossing takes the minimum 30.0 s when the boat is pointing due East.
It follows that

The boat's position
at time
is

so that after 30.0 s, the boat's final position on the other side of the river is

and the boat would have traveled a total distance of

Answer:
Please provide an image to help clarify
Explanation:
thanks :)
Answer:
C). Refraction
Explanation:
When light enters from one medium to another medium then it changes it's direction from its initial direction
the phenomenon of changing the direction due to change in the medium is known as Refraction of light
So here we know that when light strikes an interface which separates two medium then due to change in the medium we will have

so here we have
= two angles of the light in two mediums
= two refractive index of the two mediums
So correct answer will be
C). Refraction
De-celleration because speed is lower as time goes on
Answer:
The algebraic equation is:

Explanation:
Given information:
mb = book's mass
vb = tangential speed
R = radius of the path
Question: Derive an algebraic equation for the vertical force, Fv = ?
To derive the equation, we need to draw a force diagram for this case, please, see the attached diagram. As you can see, there are three types of forces acting on the system. Two up and one of the weight acting down. Therefore, the algebraic equation is as follows:

The variables were defined above and g is the gravity.