Astudent slides a book across a desk, with a velocity of +8 m/s. when her friend catches the book, it has a velocity of +7.4 m/s. if the acceleration was a constant -5.6 m/s2, how wide is the desk? a. 0.05 m b. 0.60 m c. 0.83 m d. 1.65 m

Because acceleration was constant throughout the slide, we can show the slide lasted

Also because accleration was constant, we know the average velocity of the book was

Average velocity is also given by

so the width of the desk must have been

which means C is the most likely answer.

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.