The mass of the knife which is kept on the meter stick is 66 grams.
The mass of the two coins = 2 x 5 g
= 10 g
The position of the coins is at the 0.12 m mark
The position of the knife is at the 0.45 m mark
The length of the meter stick is 0.5 m
The mass of the knife can be found using the formula,
M = (x₂ - x₁)m / (x₃ - x₁)
where M is the mass of the knife
m is the mass of the coins
x₁ is the position of the coins
x₂ is the position of the knife
x₃ is the length of the knife.
Let us substitute the known values in the above equation, we get
M = (0.45 - 0.12)(10) / (0.5 - 0.45)
= (0.33)(10) / 0.05
= 3.3 / 0.05
= 66 g
Therefore, the mass of the knife is 66 gram
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