# A person travels by car from one city to another with different constant speeds

• r-soy
In summary, a person travels a total distance of 220 km with different constant speeds between pairs of cities, driving for 30 minutes at 80 km/h, 12 minutes at 100 km/h, and 45 minutes at 40 km/h and spending 15 minutes eating lunch and buying gas. The average speed for the trip is 1.4511 km/h. The distance between the initial and final cities along the route is 220 km.
r-soy
A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 30.0 min at 80.0 km/h, 12.0 min at 100 km/h, and 45.0 min at 40.0 km/h and spends 15.0 min eating lunch and buying gas. (a) Determine the average speed for the trip. (b) Determine the distance between the initial and final cities along the route.

I try to solve

(a) Averge speed = total distance / total time

= 30 + 12 + 45 + 15 / 80.0 + 100 + 40.0 = 0.1673 km/h

(b) The distance

= 80 + 100 + 40 = 220 km

This is wrong. How far do you get driving 30 minutes at 80 km/h?

which one is wrong and I fo same the

Averge speed = total distance / total time

??

I try to solve agine

(a) Averge speed = total distance / total time

now i try to convert all the time to hour
by using 1 h = 60
30 /60 = 0.5 and 12/60 = 0.2 and 45/60 = 0.75 and 15/60 = 0.25

0.5 + 0.2 + 0.75 + 0.25/ 80.0 + 100 + 40.0 = 1.4511 km/h

(b) The distance
= Distance = velocity / time =
1 ) 40 - 12 / 1.95 = 14.35 m/s

where are you ?

you know
Averge speed = total "distance" / total time

are you sure that's what you have done in your solution?

r-soy said:
where are you ?

I drove my wife to the doctor and later we went shopping. You see, I have a life outside PF.

Summing speeds is not a way of calculating distance.

The only thing you approached correctly so far was calculation of total time.

No idea why you try to calculate average speed dividing time by the distance, instead of distance by the time.

To calculate total distance you have to separately calculate distance covered with each speed, then sum them. For example, if you drive for half an hour at 40 km/h and then for 15 minutes at 100 km/h, you cover 0.5h*40km/h=20km in the first leg and 0.25h*100km/h=25km in the second leg, total of 45 km.

## 1. How does the speed of the car affect the travel time?

The speed of the car directly affects the travel time. The faster the car travels, the less time it will take to reach the destination. For example, if a car travels at a constant speed of 60 mph, it will take 2 hours to travel 120 miles. However, if the car travels at a constant speed of 30 mph, it will take 4 hours to travel the same 120 miles.

## 2. Can the travel time be calculated if the distance and speed are known?

Yes, the travel time can be calculated using the formula: Time = Distance / Speed. This formula is applicable when the car travels at a constant speed throughout the journey. For example, if the distance between two cities is 200 miles and the car travels at a constant speed of 50 mph, the travel time will be 4 hours.

## 3. How does the average speed of the car differ from the constant speed?

The average speed of a car is the total distance traveled divided by the total time taken. This can differ from the constant speed if the car travels at different speeds during the journey. For example, if a car travels at a speed of 50 mph for the first half of the journey and then at a speed of 70 mph for the second half, the average speed will be 60 mph, but the constant speed will be 50 mph.

## 4. Can a car travel at a constant speed throughout the journey?

In theory, a car can travel at a constant speed throughout the journey. However, in reality, there can be various factors such as traffic, road conditions, and weather that can affect the car's speed. Therefore, it is difficult for a car to maintain a constant speed throughout the journey.

## 5. How does the distance between two cities affect the travel time?

The distance between two cities directly affects the travel time. The longer the distance, the longer the travel time will be. For example, if a car travels at a constant speed of 60 mph, it will take 2 hours to travel 120 miles, but it will take 4 hours to travel 240 miles at the same speed.

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