Answer:
The focal length of the lens must be 27.3cm
Explanation:
Image distance= -75 cm
Object distance= 20.0cm
From:
1/v + 1/u = 1/f
-1/75+ 1/20 = 1/f
11/300= 1/f
f= 300/11
f= 27.3cm
The focal length of the lens must be 27.3cm
Answer:
Explanation:
For an electric force, F the formula:
F = kQq/r^2
Given:
r2 = 1/2 × r1
F1 × r1 = k
F1 × r1 = F2 × r2
F2 = (F1 × r1^2)/(0.5 × r1)^2
= (F1 × r1^2)/0.25r1^2
= 4 × F1.
Answer:
Explanation:
Given
mass of children 
distance between two children 
suppose small child is at a distance of x m from pivot point
so torque of small child and heavier child must be equal
Answer:
lithium
Explanation:
A lithium atom contains 3 protons in its nucleus irrespective of the number of neutrons or electrons. Notice that because the lithium atom always has 3 protons, the atomic number for lithium is always 3. The mass number, however, is 6 in the isotope with 3 neutrons, and 7 in the isotope with 4 neutrons.
