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7/29/2019 Sdt excelsior

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SPEED AND DISTANCEAUGUST 2012Poornima Day 7

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BASIC CONCEPTS

Speed = Distance/Time

If speed is same then distance is directly proportional to

time

If time is same then distance is directly proportion to

speed

If distance is same then time is inversely proportional to

speed

1 km/h = 5/18 m/s

Average speed = Total distance/Total time



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If equal distances are covered at speeds u and v, then

average speed = 2uv/(u+v)

If distances in the ratio m:n are covered at speeds u and

v, then average speed = (m+n)uv/(mv+nu)

Relative speed in same direction= u-v & different

direction=u+v

If u and v are downstream and upstream speeds of

boat, then

Speed of boat in still water = (u+v)

Speed of stream = (u-v)



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PROBLEMS

If a person walks at 20 km/hr instead of 10

km/hr, he would have walked 20 km more.

The actual distance travelled by him is:

A. 30 km

B. 10 km

C. 20 km

D. 40 km


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Walking at 1/4 of his usual speed, a man is

late by 2 hr. The usual time is.

A 40 minutes

B 20 minutes

C 30 minutesD 60 minutes


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A train covers a distance in 50 min ,if it runs

at a speed of 48kmph on an average. The

speed at which the train must run to reduce

the time of journey to 40min will be.

A 60 Kmph

B 50 Kmph

C 70 Kmph

D 80 Kmph


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Excluding stoppages, the speed of a bus is 30

kmph and including stoppages, it is 20 kmph.

For how many minutes does the bus stop per

hour?

A 30 minutes

B 20 minutes C 10 minutes

D Cant be determined


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The average speed of a bus without stoppages is 40

kmph and with stoppages is 26 kmph. How many

minutes does the bus stop in an hour?


a) 21 minutes

b) 24 minutes

c) 30 minutes

d) Cannot be determined


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A man complete a journey in 3 hours. He travelsfirst half distance of the journey at the rate of100 km/hr and second half distance at the rate

of 50 km/hr. Find the total journey in km.

A 200 Km

B 225 Km

C 175 Km

D 250 Km


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The ratio between the speeds of two trains is

7 : 8. If the second train runs 800 km in 4

hours, then the speed of the first train is:

A 200 kmph

B 175 kmph

C 150 kmph

D 225 kmph


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In covering a distance of 30 km, Raj takes 2hours more than Vikram. If Raj doubles hisspeed, then he would take 1 hour less than

Vikram. Raj's speed is:

A 5 kmph

B 6 kmph

C 6.25 kmph

D 7.5 kmph


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A train, whose length is 100m crosses a

platform in 20 seconds while running at a speed

of 90 kmph. Find the length of the platform.

A 400 m

B 1700 m

C 500 m

D 600 m


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A train travelling with uniform speed crosses aplatform of length 800m in 20 seconds and atunnel of length 1.1 km in 25 seconds. What is

the length of the train?

A 400m

B 300m

C 250m

D 320m


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Walking at 40% more than my usual speed, I

reach my office six minutes early. Find my

usual time to reach my office.

A 21 minutes

B 20 minutes

C 15 minutes

D 18 minutes


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Two men start at the same time and walk acertain distance at 12/5 kmph and 9/4 kmphrespectively. The former arrives 5 minutesbefore the latter. What is the distance they havewalked?

A 2 km

B 3 km

C 5 km

D 6 km


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After travelling a distance of 180km a train met withan accident and travelled at 3/4th speed and hencewas late by an hour. If the accident had occurred aftermoving 60 km from the place of accident, the delaywould have been 30 minutes. What is the totaldistance travelled by the train?

A 120 km

B 180 km

C 240 km

D 300 km


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If 460 poles are arranged such that the distance

between any two consecutive poles is 20m and a train

180m long crosses them completely in 3 minutes, what

is the speed of the train?


a) 52 m/s

b) 50 m/s

c) 55 m/s

d) 60 m/s


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Two people Amar and Vikram leave the samecamp and run in east and west directionsrespectively. Amar runs at 2kmph and Vikramruns at 1kmph. After 1 hr they both travel in east

direction. How far apart are they after 2 hour?

A 3 km

B 4 km

C 0 km

D 5 km


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A person can row 12km downstream in 12

minutes and return in another 18 minutes.

What is the speed of the stream?

a) 5 km/hrb) 10 km/hr

c) 8 km/hrd) 12 km/hr

f b k /E l i Ed ti


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A train leaves Chennai at 6 AM and reaches Bangalore

at 10 AM. Another train leaves Bangalore at 8 AM and

reaches Chennai at 11:30 AM. At what time do the two

trains meet?


a) 8:45 AM

b) 8:56 AM

c) 9:05 AM

d) 6:56 AM


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A train running at a uniform speed crosses

two men coming from the opposite direction

at 18kmph and 36kmph in 16 seconds and

12 seconds. What is the speed of the train?

a) 30 kmph

b) 36 kmph

c) 40 kmph

d) 45 kmph


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If a train of length L1, moving with a speed v,crosses another train of length L2 moving withspeed u (v>u), how much time would berequired for crossing if trains are moving in

opposite direction. Consider L1 > L2

A 2(L1 + L2) / (v+u)

B (L1

+ L2

) / (v-u)

C (L1 + L2) / (v+u)

D (L1 - L2) / (v+u)


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In a race of 600m, A can beat B by 60m and

in a race of 500m, B can beat C by 25m. By

how many meters will A beat C in a race of

400m?

a) 50m

b) 55m

c) 58m

d) 60m

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In a 1000m race, A beats B by 100m and C by 200m. If

A takes 50 seconds to finish the race, what is the ratio

of the times taken by A, B and C to finish the race?


a) 36:40:45

b) 8:9:10

c) 10:9:8

d) 30:40:50


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CIRCULAR MOTION

Two people A & B moving in a circular path,

starting from same point at same time.

Opposite direction

Their relative speed is the sum of their speeds.

In interval between one meeting of A&B and their

next meeting, the total distance covered by both

of them together is equal to length of track


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Same direction

Their relative speed is the difference of their

speeds.

In interval between one meeting of A&B and theirnext meeting, the faster person covers one

complete round more than slower person


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Time for meeting in circular motion

Two people A & B moving in a circular path oflength L, starting from same point at same

time with speed a and b respectively.Same direction

Meeting first time at any point L / (a b)

Meeting first time at starting point LCM (L/a, L/b)

Opposite direction Meeting first time at any point L / (a + b)

Meeting first time at starting point LCM (L/a, L/b)


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Consider a circle with circumference 200 metresand two people A and B moving in clockwisedirection with speeds 10m/s and 25m/s. Afterhow much time will they meet for the first time.

A 5.71 s

B 13.33 s

C 8 s

D They will never meet


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Consider a circle with circumference 200 metresand two people A and B moving in samedirection with speeds 10m/s and 25m/s. Afterhow much time will they meet first at the startingpoint.

A 20 s

B 40 s C 80 s

D 160 s


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In a circular path of length 100 m, two people Aand B are starting from different point andmoving in opposite direction with a speed of 1m/s and 4 m/s respectively, meet for the first

time in 15 sec. Find the initial separationbetween them.

A 25 m

B 65 m C 15 m

D Cannot be determined


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A, B and C run along a circular track having a lengthof 1.2 km, with speeds of 6 km/hr, 8 km/hr and 9km/hr respectively. A and B run in the same directionbut C runs in opposite direction. If they all start at thesame time and from same place, how many times will

A and C meet anywhere on the track by the time Aand B meet for the first time any where on the track.

A 5 times

B 6 times C 7 times

D 8 times

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