Awoman drives a car from one city to another with different constant speeds along the trip. she drives at a speed of 50.0 km/h for 25.0 min, 95.0 km/h for 20.0 min, makes a stop for 40.0 min, then continues at 40.0 km/h for 30.0 min, at which point she reaches her destination.
a) what is the total distance between her starting point and destination (in km)b) what is the avg speed for the entire trip in (km/h)

A) 72.4 km

To calculate the total distance, we have to calculate the  length of each part of the trip.

Part 1):

v = 50.0 km/h

t = 25.0 min = 0.42 h     (25/60)

Part 2):

v = 95.0 km/h

t = 20.0 min = 0.33 h      (40/60)

Part 3):

The woman stays constant for t = 40.0 min, so no distance covered in this part.

Part 4):

v = 40.0 km/h

t = 30.0 min = 0.5 h      (30/60)

So the total distance covered is

B) 37.7 km/h

To find the average speed for the entire trip, we have to divide the total distance by the total time taken.

The total time taken is

Converted into hours,

And the total distance is

d = 72.4 km

So the average speed is

Explanation:

We should know that

Speed = distance traveled/time taken

S= d/t

Then,

d = S×t

distance = speed × time

A woman drives in a city with different speed

1. She drives at

50km/hr for 25mins

Distance = speed × time.

Distance = 50km/hr × 25/60 he

Distance. = 20.833km

2. 95km/hr for 20mins

Distance = s × t

distance = 95km/hr × 20/60 hr

Distance = 31.667km

3. She stopped for 40mins, with traveling

t = 40mins.

4. She continue at 40km/hr for 30mins

Distance = speed × time

distance = 40km/hr × 30/60

Distance = 20km

A. Total distance travelled

We are going to add all the distance traveled from one point to another

Total distance = 20.833 +31.667+20

Total distance = 72.5 km

B. Average speed?

Average speed is the total distance divided by the total time taken, the time she used to stop will be added.

Total time taken is

T = 25 + 20 + 40 + 30

T = 115 mins

T = 115/60 = 1.917 hr

So,

Average speed = total distance / total time taken

A.S = 72.5 / 1.917

A.S = 37.83 km/hr

hypothesising or postulating

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.