Answer:
a)
& 
b) 
c) 
Explanation:
Given:
mass of the book, 
combined mass of the student and the skateboard, 
initial velocity of the book, 
angle of projection of the book from the horizontal, 
a)
velocity of the student before throwing the book:
Since the student is initially at rest and no net force acts on the student so it remains in rest according to the Newton's first law of motion.

where:
initial velocity of the student
velocity of the student after throwing the book:
Since the student applies a force on the book while throwing it and the student standing on the skate will an elastic collision like situation on throwing the book.

where:
final velcotiy of the student after throwing the book
b)



c)
Since there is no movement of the student in the vertical direction, so the total momentum transfer to the earth will be equal to the momentum of the book in vertical direction.



Answer:
E = 31.329 N/C.
Explanation:
The differential electric field
at the center of curvature of the arc is
<em>(we have a cosine because vertical components cancel, leaving only horizontal cosine components of E. )</em>
where
is the radius of curvature.
Now
,
where
is the charge per unit length, and it has the value

Thus, the electric field at the center of the curvature of the arc is:


Now, we find
and
. To do this we ask ourselves what fraction is the arc length 3.0 of the circumference of the circle:

and this is
radians.
Therefore,

evaluating the integral, and putting in the numerical values we get:


If the question is true or false then the answer is true
An object will stay in motion unless acted upon by an UNBALANCED force.