Question

A woman 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)

Answer 1

Step-by-step 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

Answer 2

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)

`d_1 = vt=(50.0)(0.42)=21 km`

Part 2):

v = 95.0 km/h

t = 20.0 min = 0.33 h (40/60)

`d_2 = vt=(95.0)(0.67)=31.4 km`

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)

`d_4 = vt=(40.0)(0.5)=20 km`

So the total distance covered is

`d=d_1 +d_2+d_4=21+31.4+20=72.4 km`

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

`t=25.0 + 20.0 +40.0 +30.0 =115.0 min`

Converted into hours,

`t=(115)/(60)=1.92 h`

And the total distance is

d = 72.4 km

So the average speed is

`v=(d)/(t)=(72.4)/(1.92)=37.7 km/h`