The focal length of a bi-convex thin lens is 10 cm. The focal length of a convex-concave thin lens is -20 cm. If placing them in parallel and in close contact, the compound focal length in cm is

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2

hi there!

out of the two, (b) precision would be more reasonable.   however, both a and b could be pretty reasonable.

-awesomerepublic   : )