1) A scooterist covers a distance of 3 km. in 5 min. calculate his speed in:
a) centimeters per s.
b) m./s
c) km/h
2) The train 'A' traveled a distance of 120 km in 3 hours whereas another train 'B' traveled a distance of 180 km in 4 hours. Which train traveled faster?
3) A car travels 30 km at a uniform speed of 40km/h and the next 30 km at a uniform speed of 20km/h. Find its average speed?
4) On a 120 km track, a train travels the first 30 km at a uniform speed of 30km/h. How fast must the train travel the next 90 km so as to average 60km.h for the entire trip? Also mention your solution with a diagram.
5) A train travels at a speed of 60km/h for 0.52h, at 30km/h for the next 0.24h and then at 70km/h for the next 0.71h. what is the average speed of the train?
Anandita Dalal
Q.2) train A
distance = 120 km
time = 3 hr
speed = distance/time
= 120/3
= 40 km/h ans
train B
distance = 180 km
time = 4 hr
speed = distance/time
= 180/4
= 45 km/h ans
hence , train b traveled faster
Q.3) A
distance = 30 km
speed = 40 kmh-1
time = distance/speed
= 30/40
= 0.75 hr
B
distance = 30 km
speed = 20km/h
time = distance/speed
= 30/20
= 1.5 hr
hence,
average speed = total distance / total time
= (30+30)/(1.5+0.75)
= 60/2.25
= 26.66 km/ hr ans
Q.4) a
speed = 60 km/h
time = 0.52 h
distance = speed*time
= 60*0.52
= 31.2 km
b
speed = 30 km/h
time = 0.24 h
distance = speed*time
= 30*0.24
= 7.2 km
c
speed = 70 km/h
time = 0.71 h
distance = speed*time
= 70*0.71
= 49.7 km
hence,
average speed = total distance / total time
= (31.2+7.2+49.7)/(0.52+0.24+0.71)
= 88.1/1.47
= 59.93 km/ hr ans
PANKAJ
IX-C
hii.. how r u
answers are :-
Q.1)
a) centimeter / second (cms-1)
distance = 3 km
= 3*100000
= 300000 cm
time = 5 min
= 5*60
= 300 sec
speed = distance/time
= 300000/300
= 1000 cm/s ans
b) meter / second (ms-1)
distance = 3 km
= 3*1000
= 3000 m
time = 5 min
= 5*60
= 300 sec
speed = distance/time
= 3000/300
= 10 m/s ans
c) kilometer / hour (kmh-1)
distance = 3 km
time = 5 min
= 5/60
= 0.083 hr
speed = distance/time
= 3 / 0.083
= 36.14 km/h ans
PANKAJ
IX-C
for other questions wait..
PANKAJ
IX-C
Hi Pankaj your answer for the 1st question c) part is wrong please try it once more.
Regards
Anandita Dalal
hi anandita , i have tried Q.1 c part again , but i had got the same answer .
PANKAJ
IX-C
Hi Pankaj !!!!
For your convenience there is a hint that the answer is 36km/h . Now try to find the answer, if you fail then I will give you the solutions for it.
Regards
Anandita Dalal
Hi Pankaj i have seen your solution according to me there is a calculation mistake. To do it in an easy way and get the correct answer you can divide it by 5/60 it self.
Regards
Anandita Dalal
1) A body travels a distance of 15 m due north and then distance of 20 m due east. Calculate the total distance and displacement.
hii..! anandita , by your method i have got 36 only but my calculations are not wrong , my answer 36.14 is standard . i have not estimated my answer , we are in now senior class now we should concentrate on the standard things.
PANKAJ
IX-C
Hi Pankaj I truly agree on your point of standard things , I have tried your method on the calculator and the answer was 36 only.
Regards
Anandita Dalal
hi..
your answer is:-
let the initial position be A
15m towards north , let the next point be B , 20 m towards east ,
let the final position be C
so,
distance = AB+BC
= 15+20
= 35m
displacement => AB2+BC2 =AC2 (By pythogorus theorum)
=> 152 +202 = AC2
=> 225+400 = AC2
=> 625 = AC2
=> 25 m = AC (Transporting square another size)
PANKAJ
IX-C