What Is the Average Speed of a Car on a Round Trip?

[huma]

Homework Statement

a car starts from hither , goes 50km in a straight line to yon , immediately turns around, and turns to hither . the time for this round trip is 2 hours . the average speed of the car for this round trip is ?

Homework Equations

average velocity = disrance covered /time

The Attempt at a Solution

as the body comes back to its initial position so average velocity is zero ... but answer key shows the right answer is 50 km/hr ....I can't understand ... what you think what is correct answer

 

[berkeman]

Homework Statement

a car starts from hither , goes 50km in a straight line to yon , immediately turns around, and turns to hither . the time for this round trip is 2 hours . the average speed of the car for this round trip is ?

Homework Equations

average velocity = disrance covered /time

The Attempt at a Solution

as the body comes back to its initial position so average velocity is zero ... but answer key shows the right answer is 50 km/hr ....I can't understand ... what you think what is correct answer

It sounds like they are asking for average speed, not average velocity. Your equation you list is for average speed, not average velocity.

And 50km/hr looks to be a wrong answer, since the time elapsed is 2 hours. Are you sure you have written the problem and answer correctly?

EDIT -- I misread the problem, and now see why they got 50km/hr.

 

[huma]

ohhhh yesh its my mistake I write wrong equation ...average speed = total speed /time ... what you think now my answer is correct or wrong ?

 

[Chestermiller]

The car travels 100 km in 2 hr, so its average speed is 50 km/hr. But, as berkeman points out, the question asks for the average speed, not the average velocity.

 

[Mark44]

ohhhh yesh its my mistake I write wrong equation ...average speed = total speed /time ... what you think now my answer is correct or wrong ?

This equation -- average speed = total speed /time -- is meaningless (and wrong). There is no such thing as "total speed".
The corrected equation is speed = (total distance)/(elapsed time).
For velocitiy, it is velocity = (total displacement)/(elapsed time).
In your calculation, since the car started from and returned to the same point, the total displacement is 0, so the velocity is 0. That's not what they asked for, though.