Answer: A
si, di, are expressed as negative and f is expressed as positive values.
Explanation:
When the object is located at a location in front of the focal point of a convex len, the image will always be located somewhere on the same side of the lens as the object. The image is located behind the object. In this case, the image will be an upright image and the image is enlarged
In this question, the relationship between the focal length, image distance di and object distance is
I/f = 1/di + 1/do that is
I/f - 1/di - 1/do = 0
The image size si is also negative since the image is a virtual image.
Therefore, si, di, are expressed as negative, f is expressed as positive values.
Answer:
The required work done is 
Explanation:
Consider 'F' is the applied force on the crate and 'f' be the force created by friction. According to the figure if '
' be the coefficient of friction, then

where 'M', 'N' and 'g' are the mass of the crate, the normal force aced upon the block and the acceleration due to gravity respectively.
Since the application of force by the movers does not create any acceleration to the block, we can write

So the work done (W) in moving the crate by a distance s = 10.6 m is

It depends on the objects chemical composition.
Answer:
a) i₈ = 0.5 i₄, b) i₁₀ = 0.3 i₃, i₁₀ = 0.8 i₈
Explanation:
For this exercise we use ohm's law
V = i R
i = V / R
we assume that the applied voltage is the same in all cases
let's find the current for each resistance
R = 4 Ω
i₄ = V / 4
R = 8 Ω
i₈ = V / 8
we look for the relationship between these two currents
i₈ /i₄ = 4/8 = ½
i₈ = 0.5 i₄
R = 3 Ω
i₃ = V3
R = 10 Ω
i₁₀ = V / 10
we look for relationships
i₁₀ / 1₃ = 3/10
i₁₀ = 0.3 i₃
i₁₀ / 1₈ = 8/10
i₁₀ = 0.8 i₈