Answer:
The number of pencils that needs to be placed at the other 1 inch end to get a balance again is approximately 3 pencils
Step-by-step explanation:
The given parameters are;
The length of the ruler used as a seesaw = 12 inch
The location where the pencil is placed = Under the 4 inch mark
The location where the weight is placed to balance the seesaw = The 2 inch mark
Therefore, the pencil at the 4 inch mark is fulcrum
The location where a pencil is placed on the ruler = The 12 inch end
The number of pencils, x, that needs to be placed at the other 1 inch end to get a balance again is given as follows;
The distance of the pencil at the 12 inch end from the fulcrum = 12 inches - 4 inches = 8 inches
The distance of the pencils placed at the 1 inch end from the fulcrum = 4 inches - 1 inch = 3 inches
Therefore at balance point, (equilibrium) the anticlockwise moment = The clockwise moment, which gives;
The mass of 1 pencil × 8 inches = x × The mass of 1 pencil × 3 inches
x = (The mass of 1 pencil × 8 inches)/(3 inches × The mass of x × 1 pencil)
x = 8/3 = 2. ≈ 3 pencils
The number of pencils that needs to be placed at the other 1 inch end to get a balance again = x ≈ 3 pencils.