How much energy is needed to keep a 9 watt light bulb lit for 8sec?

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.

Why should seat belts not be mandatory quick plz

Why is it important always to use horizontal bars in unit fractions when performing unit conversions?