Answer:
At the focus
Explanation:
In car head lights concave mirrors are used. The light bulbs in these headlights are place along the principal axis as shown in the figure. On this Principal axis light bulbs are place at the Focus to get maximum brightness. As from the figure we can conclude that light rays coming from infinity converse at focus thus, giving maximum brightness.
Recall that
The car starts from rest, so 
, and we get
The change in electric potential energy of the ion is equal to the charge multiplied by the voltage difference:
where the charge q of the na+ ion is equal to one positive charge, so it's equal to the proton charge:
, and Vf and Vi are the final and initial voltages.
Substituting the numbers, we find:
Answer:
(D) 42.4N
Explanation:
Since the frame is at rest, the net force acting on it must be 0. There are three forces acting on it: the gravity and the opposing forces of the two cables.
Since the gravity is a vertical force, we are only interested in the vertical components of the remaining forces. The net force equation is
F_net = 0 = F_g -2 * F_y
The vertical force of one cable (using the information in the drawing) is:
F_y = 30N * sin 45 deg = 21.21N
Now the weight can be determined:
0 = F_g - 2 * F_y
F_g= 2 * F_y = 2 * 21.21N = 42.4N
The weight of the frame is about 42.4N.
