Chapter 3: Boat and Stream
📝Chapter 3: Boat and Stream
Introduction: He zirlai hi MPSC, SSC ,UPSC leh Competitive exam hrang hrang bei tur te tan a pawimawh em em a, He zirlai a problem solve sa loh pawh hi a last page ah ka dah tho a kan lo try ve chhin dawn nia. Competitive exam na a pawimawh thei tur ang ber lak khawm a ni.
Written by: Elisa Lalrinngheta ( Zo Guide founder)
@Copyright Reserved by the author
Stream leh Boat hian physics leh maths-ah hian hmun pawimawh tak a chang a ni.
Q.🤷Eng nge stream leh boat chu ?
✅Stream: Tui luang (lui, khawh, etc.) a ni. Stream hi object a kalna tur kawng leh chak dan sawina a ni.
✅Boat: Tui chunga kal thei, lawng, etc. a ni. Boat hi stream-a kal a, stream-in a kalna tur kawng leh chak dan a nghawng a ni.
Entirnan:
- Boat-in stream-a a kal chak dan leh stream-a tui luang chak dan inang lo a nih chuan, boat a kal chak dan leh a kal dan kawng a dang a ni.
- Stream-a tui luang chak dan leh boat a kal chak dan a inang a nih chuan, boat a kal chak dan leh luiluanh chak dan an ang a ni
Lawng leh tui luang (Boat and Stream) hian luipui emaw luitea tui luang chunga lawng chevel chungchang harsatna leh inzawmna a tarlang a. Heng harsatnate hian inmil taka chakna (relative speed) ngaihruatna an tel a, tui current chakna a lawng chet chakna a nghawng dan a zirin, a current nen a intawm emaw a inkalh emaw a ni thei. Lawng chakna leh current chakna inzawm dan hriatthiam hi heng harsatnate chinfel nan hian a pawimawh hle.
✅Hriat ngei ngei tur thil te:
1. Stream or Speed of Stream: Hei hi luipui emaw luitea tui luang( current ) chakna a ni. A tlangpuiin S tia sawi thin a ni. Current hian lawng chet chakna a nghawng a, a kalna lam a zirin.
🤔 Current awmzia- tui luang, kal lai, awm mek,etc
2.Upstream (Tui luang chunga chho): He thu hian luipui emaw luitea tui current luang kalh zawnga kalna a kawk a. Lawng emaw bungrua engemaw Upstream zawnga a kal chuan, tui current a kalh a ni a, Downstream zawnga kal aiin tha tak zawk leh chakna a ngai zawk thin. Upstream zawnga lawng chet chakna hi a tlangpuiin current chakna hian a tihniam thin.
3.Downstream (Tui luang chunga chhuk): He thu hian luipui emaw luitea tui current luang zawnga kalna a kawk a. Lawng emaw bungrua engemaw Downstream zawnga a kal chuan, tui current a zawm a ni a, Upstream zawnga kal aiin zin a awlsam zawk a, a chak zawk thin. Downstream zawnga lawng chet chakna hi a tlangpuiin current chakna hian a tipung thin.
4.Tui ding (Still Water): Tui chevel lo anga ngaih, a chakna zero a ni.
🤷Hriat ngei ngei tur Formula:
1.Tui ding chhunga lawng chakna: B
2.Luipui current chakna: S
🤷Tun ah chuan Example te kan lo en ho tawh ang:
Q. A man takes half time in rowing a certain distance downstream than upstream. What is the ratio of the speed in still water to the speed of current? [CSAT UPSC: 2020]
(a) 1:2
(b) 2:1
(c) 1:3
(d) 3:1✅
Answer: (d)
Solution:
Given that,
Time taken downstream = (1/2) time in upstream
Let,
Speed of boat = B km/hr
Speed of stream = S km/hr
Distance covered = D km
Now,
Downstream = (B + S) km/hr
Upstream = (B - S) km/hr
2D/(B + S) = D/(B - S) .....(GIVEN)
B = 3S
Thus B/S = 3/1
Therefore the required ratio = 3 : 1
Hence option (d) is correct
✅ More Examples:
✅Case 2:
Hmun hlat zawng inangah, tui luanna chho zawnga kal turin, tui luanna hnuai zawnga kal aiin T hours a duh zawk chuan:
Hemi case bik ah hian example lo en leh ta ila:
Case 3: Lawng Pakhat chu tui luanna chhuk zawng lam pan in T₁ hours chhunga hla a kal a, lui luang chho na lam zawngin T₂ hours chhunga hla a rawn let leh a, S chu luia tui chak zawng a nih chuan:
🕵️Tun ah chuan hetiang ang case 3 bik ah Example lo en ho leh ta ila:
✅Case 4:
Boat-in stream a zawh hun downstream chu T₁ leh upstream chu T₂ a nih chuan,
Boat chak dan leh stream chak dan inzatna chu:
(T₂ + T₁) : (T₂ - T₁)
💆Hetiang ang type Questions kan lo en ho leh phawt ang
🕵️Example: A boat takes half time in rowing a certain distance downstream than upstream. What is the ratio of the speed of a boat in still water to the speed of current?
✍️Solutions:
🕵️Example : A boat covers a certain distance downstream in 4 hours but takes 6 hours to return to the starting point. What is the ratio of the speed of the stream to the speed of the boat in still water?
Solution:
Let distance be d km. Let speed of the boat and stream be x km/hr and y km/hr. → Upstream speed = (x - y) → Downstream speed = (x + y) According to the question d / (x - y) = 6 d / (x + y) = 4
➡️ d = (x + y)× 4 ...ii) From equation (i) and equation (ii) 6(x - y) = 4(x + y)
➡️ d = (x - y) × 6 ______. i)
➡️ 6x - 6y = 4x + 4y
➡️ 6x - 4x = 6y + 4y
➡️ 2x = 10y
⇒x: y = 5/1
.. The correct answer is y / x = 1/5
___________________________
Example 9: A boat can travel 200 km upstream in 10 hours. If it increases its speed in still water by 10 km/hr, it can travel 140 km downstream in 2 hours. Find the speed (in km/hr) of the stream.
Solution:
🕵️Practice Questions: ( the following questions are repeated questions for competitive exam)
Q1.A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.
1).2 hours
2).3 hours
3).4 hours
4).5 hours
2.A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is:
A)8.5 km/hr
B)9 km/hr
C)10 km/hr
D) 12.5 km/hr
3.A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?
1) 2 : 1
2) 3 : 2
3) 8 : 3
4) Cannot be determined
5) None of these
4.In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
1) 3 km/hr
2) 5 km/hr
3) 8 km/hr
4) 9 km/hr
. . . . . . .. . . . .
🤷Answer with explanation:
1. Ans:
2. Ans:
4.Ans:
