A man walks on a straight road from his home to a market 3km away with a speed of 6 km/h , finding the market closed instantly turns and walks back with a speed of 9 km/h. what is the (a) magnitude of average velocity and average speed of the man over the interval of time (i) 0 to 30 minutes,(ii) 0 to 50 minutes (iii) 0 to 40 minutes?
Answers
Answer:
(i) 0 to 30 minutes
Average velocity = 6 km/h
Average speed = 6 km/h
..............................
(ii) 0 to 50 minutes
Average velocity = 0 km/h
Average speed = 7.2 km/h
.................................
(iii) 0 to 40 minutes
Average velocity = 2.25 km/h
Average speed = 6.75 km/h
Explanation:
given that,
A man walks on a straight road from his home to a market 3km away with a speed of 6 km/h
here,
given the distance of the market from his home = 3 km
speed by which he went = 6 km/h
so,
time taken to reach market = 3/6
= 30 minutes
also given that,
he walks back with a speed of 9 km/h.
so,
time taken by the man in returning home = 3/9
= 1/3 h
= 20 minutes,
now,
(b) Average velocity and average speed speed of the man in
(I) 0 to 30 minutes
(a) Average velocity
here,
displacement = 3
time = 30 min
= 1/2 h
so,
average velocity = 3/½
= 6 km/h
(b) Average speed
here,
distance = 3 km
time given = 1/2 h
average speed =
distance travelled/time taken
= 3/½
= 6 km/h
(ii) 0 to 50 minutes
(a) Average velocity
since displacement is 0
and
average velocity = displacement/time
so,
average velocity = 0 m/s
(b) Average speed
total path length covered = 3 + 3 = 6 km
total time taken = 50 minutes
= 50/60 h
= 5/6 h
now,
Average speed =
total distance travelled/total time taken
= 6/(5/6)
= 7.2 km/h
(iii) 0 to 40 minutes
distance moved in 30 minute (from home to market) = 3 km
distance moved in 10 minute from (market to home) with speed 9 km/h
= 9 × (10/60)
= 1.5 km
so,
displacement = 3.0 - 1.5 = 1.5 km
total path length covered = 3.0 + 1.5
= 4.5 km
(a) Average velocity
displacement/time
= 1.5/(40/60)
= 2.25 km/h
(b) Average speed
= total path length covered/time taken
= 4.5/(40/60)
= 6.75 km/h
_________________
(i) 0 to 30 minutes
Average velocity = 6 km/h
Average speed = 6 km/h
..............................
(ii) 0 to 50 minutes
Average velocity = 0 km/h
Average speed = 7.2 km/h
.................................
(iii) 0 to 40 minutes
Average velocity = 2.25 km/h
Average speed = 6.75 km/h
Answer:
(i) average velocity/speed = 6 km/h
(ii) average velocity = 0 km/h
average speed = 7.2 /h
(iii) average velocity = 2.25 km/h
average speed = 6.75 km/h
Explanation:
REFER TO THE ATTACHMENT
sorry for the bad handwriting
