17- How much work is needed for a climber in order to climb 45 m height, where his weight is 70 kg. also, calculate the power required to climb the height in 30 minutes ? g= 9,8 m. sec

Work Done= 3150J

Power= 1.75W

Explanation:

Work Done= Force x the distance travelled in the direction of the force (W= f x d)

Weight is a force, i think the qn. stated it wrongly, it should be 70N not 70kg.

Work Done= 70 x 45

=3150J

Power= Work Done/Time

=3150/(30x60)

*convert minutes to seconds since the S.I. unit of Power is joules/seconds(J/s) or watts(W)

=1.75W

answer and explanation;

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.