In the conservation of mass, mass is never created or destroyed in chemical reactions in the same way water is not created or destroyed it is only transferred from one form to another and its mass is always conserved.
Any substance that contains starch turns blue-black in presence of <u>iodine solution.</u>
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:
The escalator does more work and the elevator has a greater power output.
Explanation:
The escalator does more work on the person because it is carrying them up. It also gives the person a chance to walk up the escalator making it a little more challenging than using just an elevator. The elevator has a greater power output because it can transport a person from one floor to another in just 10 seconds where as the escalator can do it in 15.
Hope this helps!