Answer:
The focal length of the lens should be -51.5 cm (a concave lens).
Explanation:
The purpose of the lens is to make objects at 48.5 cm appear at the healthy near point. The healthy near point is 25.0 cm.
We use the lens formula

where <em>f</em> = focal length, <em>u</em> = object distance and <em>v</em> = image distance.
In this case, <em>u</em> = 48.5 cm and <em>v</em> = -25.0 cm.
<em>v</em> is negative because the image is virtual an not real. (Here, we are using the real-is-positive sign convention)


The negative sign indicates the lens is concave.
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If you put 300 J of heat into an engine with an efficiency of 0.35, how much work can be done? 3. How much energy must be put into an engine with an efficiency of 0.6 if 270 J of work are required? 4. An engine with an efficiency of 0.425 uses 1200 J of energy. Find the amount of energy wasted by the engine. 5. Calculate the efficiency of an engine operating between temperatures of 258 K and 600 K 6. An engine runs with its exhaust (cold) reservoir at a temperature of 200 K. To what temperature should the input (hot) temperature be set if an efficiency of 0.8 is desired? 7. Complete the following table of temperatures. Fahrenheit Celsius Kelvin 213 15 98.6 75 408
It a kilogram of feathers because i learned it in science