Please help Tell whether the statements are true or false. Correct the false statements

1. A force is represented by a directed line segment called force vector.

2. The magnitude of a force is measured by a balance instrument.

3. A force can change the mass of a body.

4. The force vector is characterized by three elements.

5. The length of the force vector is proportional to the magnitude of the represented force.

true true false true false

1)true

2)true

3)false

4)false

5)true

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.