Lighthouse is a tall Tower with Light Near the Top. These are often Built on Islands, Coasts or on Cliffs. Lighthouses on Water Surface Act as a Navigational aid to the Mariners and send Warning to Boats and Ships for Dangers

By admin -
A lighthouse is a tall tower with light near the top. These are often built on islands, coasts or on cliffs. Lighthouses on water surface act as a navigational aid to the mariners and send warning to boats and ships for dangers. Initially wood, coal would be used as illuminators. Gradually it was replaced by candles, lanterns, electric lights. Nowadays they are run by machines and remote monitoring.

Prongs Reef lighthouse of Mumbai was constructed in 1874-75. It is approximately 40 meters high and its beam can be seen at a distance of 30 kilometres. A ship and a boat are coming towards the lighthouse from opposite directions. Angles of depression of flash light from the lighthouse to the boat and the ship are 30 0 and 600 respectively.

i) Which of the two, boat or the ship is nearer to the light house. Find its distance from the lighthouse?
ii) Find the time taken by the boat to reach the light house if it is moving at the rate of 20 km per hour.




(I) The boat is closer to the beacon as its point of gloom is more noteworthy.

In △ ABC, tan `60^0` = `"AB"/"BC"`

⇒ `\sqrt{3}` = `40/"BC"`

∴BC = `\frac{40}{\sqrt{3}}`

= `\frac{40 \sqrt{3}}{3}` m

In △ ADB, tan 30° = `"AB"/"BD"`
⇒ `\frac{1}{\sqrt{3}}` = `40/"DB"`

∴ DB = `40\sqrt{3}`m

(ii) Time taken to cover this distance

= `\frac{60}{2000}\times 40\sqrt{3}`

= `\frac{60\sqrt{3}}{100}`

= 2.076 minutes






Social Science
Question Paper Solutions
Mathematics
Question Paper Solutions
Mathematics Basic
Question Paper Solutions
English
Question Paper Solutions
Science
Question Paper Solutions

Comments

Post a Comment

Popular posts from this blog

Explain the Role of ‘Justice Party’ in Boycotting of Council Elections | bzziii.com

By admin -
answer source Question Read the source given below and answer the questions that follows: Source : The Movement in the Towns The movement started with middle-class participation in the cities. Thousands of students left government-controlled schools and colleges, headmasters and teachers resigned, and lawyers gave up their legal practices. The council elections were boycotted in most provinces except Madras, where the Justice Party, the party of the non-Brahmans, felt that entering the council was one way of gaining some power–something that usually only Brahmans had access to. The effects of non-cooperation on the economic front were more dramatic. Foreign goods were boycotted, liquor shops picketed, and foreign cloth burnt in huge bonfires. The import of foreign cloth halved between 1921 and 1922, its value dropping from Rs. 102 crore to Rs. 57 crore. In many places merchants and traders refused to trade in foreign goods or finance foreign trade. As the boycott movement spread...
Read more

Fraction becomes 9/11, If 2 is Added to Both the Numerator and Denominator. If 3 is Added to Both the Numerator and the Denominator, it Becomes 5/6. Find the Fraction. | Bzziii.com

By admin -
A fraction becomes `9/11`, if 2 is added to both the numerator and denominator. If 3 is added to both the numerator and the denominator, it becomes `5/6`. Find the fraction. SOLUTION Let Numerator be x & Denominator be y So, Fraction is = `x/y` Given that, If 2 is added to both the numerators and denominator, fraction becomes `9/11` `"Numerators + 2"/"Denominator + 2"`= `9/11` `"x+ 2"/"y + 2"`= `9/11` 11 (`x + 2`) = 9 (`y + 2`) 11`x` + 22 = 9`y` + 18 11`x` - 9`y` = 11 - 22 11`x` - 9`y` = -4 .......(1) Also, Given that if 3 is added to both the numerator and the denominator, fraction become `5/6` `"Numerators + 3"/"Denominator + 3"`= `5/6` `"x+ 3"/"y + 3"`= `5/6` 6 (`x + 3`) = 5 (`y + 3`) 6`x` + 18 = 5`y` + 15 6`x` - 5`y` = 15 - 18 6`x` - 5`y` = - 3 .......(2) Hence, our equations are 11`x` - 9`y` = -4 .......(1) 6`x` - 5`y` = - 3 .......(2) From equation (1...
Read more

NCERT solutions for Class 11 chapter 3 - Recording of Transactions

By admin -
Chapter 3 Recording of Transactions   Short Answer 01    State the three fundamental steps in the accounting process. SOLUTION 02    Why is the evidence provided by source documents important to accounting? SOLUTION 03    Should a transaction be first recorded in a journal or ledger? Why? SOLUTION 04    Are debits or credits listed first in journal entries? Are debits or credits indented? SOLUTION 05    Why are some accounting systems called double accounting systems? SOLUTION 06    Give a specimen of an account. SOLUTION 07    Why are the rules of debit and credit same for both liability and capital? SOLUTION 08    What is the purpose of posting J.F numbers that are entered in the journal at the time entries are posted to the accounts? SOLUTION 09    What entry (debit or credit) would you make to: (a) increase revenue (b)...
Read more