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 => AB^{2}+BC^{2} =AC^{2} (By pythogorus theorum)

=> 15^{2} +20^{2} = AC^{2}

=> 225+400 = AC^{2}

=> 625 = AC^{2}

=> 25 m = AC (Transporting square another size)

PANKAJ

IX-C