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A man walks 7 km in 2 hours and 2 km in 1 hour in the same direction. a) What is the man's average speed for the whole journey? b) What is the man's average velocity for the whole journey?

Posted in Science, asked by Laureana Beanca, 6 years ago. 11576 hits.

21

Average Speed = total distance/total time

total distance = 7 km + 2km = 9 km

total time = 2 hours + 1 hour = 3 hours

Avg. Speed = 9/3 = 3 km/hour

Avg. velocity = total displacement/total time

In this case distance = displacement for same direction.

So, average velocity = 3 km/hour

Abhinav Gaur
Abhinav Gaur - 6 years ago
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10

 It is correct that the man travels 3.5 km/hr in the first 2 hours and 2km/hr in the next 1 hour. However, averaging out the two speeds to find the average velocity of the entire trip is incorrect. By averaging the two values, you are assuming that the man travelled the two velocities for equal amounts of time, which is not true.
 
To correctly figure out the problem, you must see the journey as a whole.
 
Vavg = Δx/t
 
Since you are asked to find the average velocity of the WHOLE journey, you need to find Δx for the WHOLE journey and t for the WHOLE journey.
 
Δx = 7km + 2km = 9km
t = 2 hr + 1 hr = 3 hr
 
Since the man is walking in the same direction, he is essentially walking 9 km (7km+2km) in 3 hours (2km+1km).
 
Thus,
 
Vavg = Δx/t = 9km/3 hr = 3 km/hr

Answer: The average velocity of the whole journey is 3 km/hr.

Nelson Kim
Nelson Kim - 6 years ago
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4

SPEED

speed = distance/time

find speed for first given value

speed = distance/time  = 7 Km/ 2 hours = 3.5 Km/h

Now find speed for 2nd given value

speed= distance/time = 2 Km/ 1 hours = 2 Km/h

AVERAGE SPEED

3.5 Km/h + 2 Km/h = 5.5 /2  Km/h = 2.75  Km/h

The average speed is 2.75  Km/h.

VELOCITY

V= S / t  ( where v = velocity, s = distance and t = time )

find velocity for first given value

s = 7 km

t = 2 hours

V = 7/2

V = 3.5 km/ hr

Now we find velocity for 2nd given value 

s = 2 km

t = 1 hours

V = 2/1

V = 2 km/ hr

AVERAGE VELOCITY

3.5 + 2  = 5.5 /2 = 2.75  Km/h

The average VELOCITY is 2.75  Km/h.

 

Furqan Ali
Furqan Ali - 6 years ago
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