Adriver traveling at 22m/s, slows down her 2000kg car to stop for a red light. what work is done by the friction froce against the wheels?
a. -2.2x104 j
b. -4.4x104 j
c. -4.84x105 j
d. -9.68x105 j

C -4.84× 10^5J

Explanation:

Work done = force × distance

v^2 = u^ +2as

u= 22m/s

a =10m/s^2

When the car stops the final velocity (v) =0

0= 22^2 +2×10×s

s = -484/20

s =-24.2m

Work done = force × distance

Force = mass × acceleration

Work done = 2000×10× -24.2

= -4.84×10^5J

where are the vectors ?

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.