The lens of a healthy human eye can focus onto the retina light coming from objects lying in a range of distances from 0.10 m to infinity. It does so by contracting a set of muscles that compress the lens, thereby changing its focal length. The distance between the retina and the lens is 17 mm. What is the range of focal lengths that the eye lens can attain

Explanation:

In the given case , distance between lens and retina = 17 mm

image distance v = 17 mm

object distance u = .1 m = - 100 mm

from lens formula

1 / v - 1 / u = 1 / f

1 / 17 - 1 / 100 = 1 / f

f = 20.48 mm

For object at infinity

u = infinity , v = 17 mm

from lens formula

1 / v - 1 / u = 1 / f

1 / 17 - 1 / ∞ = 1 / f

1 / 17 = 1 / f

f = 17 mm

So range of focal lengths that the eye lens can attain

is 17 mm to 20.48 mm .

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.