I’LL MARK YOU BRAINIEST IF U ANSWER PLEASE 1. suppose the government passed a law saying, 'everyone must use an electric toothbrush ." use the four criteria to assess this change in the system of brushing your teeth

2. what are two methods of support used to keep a system operating safely and efficiently

3. A police system lifts a 500-N Weight A distance of 1.5m. Marina pulls the rope A distance of 9.0m, exerting a Force of 100 N.

a) what is the mechanical advantage of this pulley system

b) What input did marina do on the road

c) what useful output did the rope do on the weight

d) what is the efficiency of the pulley system

THIS IS GRADE 8 PHYSICS PLEASE ANSWER
PLEASE ANSWER AT LEAST 1

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

365.25 earth days are in the year of a light year