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Question

Shweta starts walking from her office and walks 150 m towards the south, then she turns right and walks 80 m, and then she turns left and walks 60 m. She finally turns left and walks 280 m to reach a bank. What is the shortest distance between her office and the bank?

The correct answer is

290 m 

Calculating Shortest Distance Between Office and Bank

The problem asks us to find the shortest distance between Shweta's starting point (office) and her ending point (bank) after a series of movements. This involves finding the net displacement, which is the straight-line distance from the start to the end point, regardless of the path taken.

Analyzing Shweta's Movements

Let's break down Shweta's walk step by step:

  • Starts at the office.
  • Walks 150 m towards the South.
  • Turns Right (from facing South, Right is West) and walks 80 m.
  • Turns Left (from facing West, Left is South) and walks 60 m.
  • Finally turns Left (from facing South, Left is East) and walks 280 m to reach the bank.

Determining Net Displacement

We can represent the movements in terms of East-West and North-South directions to find the total change in position from the office.

Southward movements:

  • 150 m South
  • 60 m South

Total displacement towards South = $150 \text{ m} + 60 \text{ m} = 210 \text{ m South}$

Eastward/Westward movements:

  • 80 m West
  • 280 m East

Total displacement towards East = $280 \text{ m East} - 80 \text{ m West} = 200 \text{ m East}$ (since East > West)

So, the final position (bank) is 210 m South and 200 m East from the starting position (office).

Using the Pythagorean Theorem

The office, the bank, and a point representing the net displacement towards South and East form a right-angled triangle. The shortest distance between the office and the bank is the hypotenuse of this triangle. We can use the Pythagorean theorem to find this distance.

Let:

  • Net Southward displacement = Perpendicular side = 210 m
  • Net Eastward displacement = Base side = 200 m
  • Shortest distance (Office to Bank) = Hypotenuse = $d$

According to the Pythagorean theorem: $Hypotenuse^2 = Base^2 + Perpendicular^2$

So, $d^2 = (200 \text{ m})^2 + (210 \text{ m})^2$

Calculating the squares:

$d^2 = 40000 + 44100$

$d^2 = 84100$

To find $d$, we take the square root of both sides:

$d = \sqrt{84100}$

$d = 290 \text{ m}$

The shortest distance between Shweta's office and the bank is 290 m.

Summary of Movements and Displacement

Step Direction Distance (m) Net North-South (m) Net East-West (m)
Start (Office) - 0 0 0
1 South 150 -150 (South) 0
2 Right (West) 80 -150 (South) -80 (West)
3 Left (South) 60 -150 + (-60) = -210 (South) -80 (West)
4 Left (East) 280 -210 (South) -80 + 280 = 200 (East)
End (Bank) - - -210 (South) 200 (East)

The net displacement is 210 m South and 200 m East. Using Pythagorean theorem: $\sqrt{(-210)^2 + (200)^2} = \sqrt{44100 + 40000} = \sqrt{84100} = 290$ m.

Final Answer

The shortest distance between her office and the bank is 290 m.

Revision Table: Distance and Displacement

Concept Definition Key Characteristics How it relates to this problem
Distance Total length of the path covered during motion. Scalar quantity, always positive, depends on path. Total distance walked by Shweta is 150+80+60+280 = 570 m. (Not asked in the question)
Displacement Shortest distance between the initial and final positions. Vector quantity (has magnitude and direction), can be zero or negative, independent of path. The shortest distance between office (start) and bank (end) is the magnitude of the displacement vector.

Additional Information: Directions and Turns

Understanding directions and turns is crucial for solving navigation problems like this. Standard directions are North, South, East, West.

  • When facing North, a Right turn is East, a Left turn is West.
  • When facing South, a Right turn is West, a Left turn is East.
  • When facing East, a Right turn is South, a Left turn is North.
  • When facing West, a Right turn is North, a Left turn is South.

In this problem:

  • Starts walking South.
  • Turns Right: Now facing West.
  • Turns Left: Now facing South again.
  • Turns Left: Now facing East.

This detailed breakdown of movements helps confirm the directional components used in the displacement calculation.

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Important Questions from Direction and Distance Turns

  1. Starting from her home, a woman walks 10 km towards the west. She turns left and walks 25 km. Again she turns left and walks 10 km. After that, she again turns left and walks 5 km. How far is she from her house now?

    A. 35

    B. 20

    C. 25

    D. 40

  2. A man travels 15 km towards the east, then turns right and travels 20 km. He then turns left and travels 30 km. Finally, he takes a right turn and covers 40 km. The shortest distance between the starting point and the destination is:

  3. A man starts from point ‘O’, travels 20 km towards East to reach point ‘A’, turns right and travels 10 km to reach point 'B', turns right and travels 9 km to reach point 'C', turns right and travels 5 km to reach point 'D', turns left and travels 12 km to reach point 'E' and then turns right and travels 6 km to reach point 'F'.

    In which direction is the man facing now?

  4. Lalit walks 9 km east, turns left and walks another 8 km. He again takes a left and walks another 3 km. How far and in which direction is he now from his starting point?

  5. A boy starts from his home northward in order to go to a hotel. He took right turn and took left to reach the hotel. Which direction is the hotel facing?

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