I think its d. but im not sure
Answer:

Explanation:
Given that
At X=0 V=Vo
At X=X1 V=0
As we know that friction force is always try to oppose the motion of an object. It means that it provide acceleration in the negative direction.
We know that



So the friction force on the box
Ff= m x a

Where m is the mass of the box.
Answer:

Explanation:
-The chemical formula for Molybdenum (V) Dichromate is 
-There are 21 moles of oxygen per one mole of Molybdenum (V) Dichromate
-We apply Avogadro's constant to find the number of atoms of oxygen:

Hence, there are
Answer:
(a) 
(b) neither increasing or decreasing
(c) opposite to the flow of charge carriers
Explanation:
The current through an inductor of inductance L is given by:
(1)
(a) The induced emf is given by the following formula
(2)
You derivative the expression (1) in the expression (2):

(b) At t=0 the current is zero
(c) At t = 0 the emf is:

w, L and Imax have positive values, then the emf is negative. Hence, the induced emf is opposite to the flow of the charge carriers.
(d) read the text carefully
from one energy form to one