Explanation:
On a frictionless surface, no net external force is required to maintain uniform velocity (Newton's first law). Only to change velocity force is needed. Thus, force required is zero. If friction present, force would be needed to balance friction.
Explanation:
The power (P) of a lens indicates its converging or diverging ability. It is mathematically defined as the reciprocal of the focal length (f), provided the focal length is measured in meters. The formula is P = 1 / f(in meters). The SI unit of power for a lens is the Diopter (D). A focal length of 0.5m gives a power of 2D.
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