I need help with more science homework I don’t know if it’s right or wrong so I need help

The velocity of car is 80.0 miles per hour. what is the velocity of car in meters per second? (1 km -0.621 miles) m/s

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.

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.