CAT Problems on Trains - Practice Questions & MCQ

Explanation:

Train problems are a popular subset of time, speed, and distance problems in competitive exams. These problems can involve one or more trains, crossings, bridges, platforms, and even other moving or stationary objects.

The most common scenarios are:

1. A train crossing a stationary object (e.g., a pole, a person).

2. A train crossing another moving object (e.g., another train, a person walking).

3. A train crossing a platform, bridge, or tunnel.

The basic principle remains the same: use the relation S = DT , but with a clear understanding of what constitutes the 'distance' in each scenario.

Foundation Building Questions :

Question: A train 400 metres long is moving at a speed of 20 m/s. How long does it take to cross a 200 metres long platform?

Solution:

Total distance to be covered by the train = Length of the train + Length of the platform

 D = 400 + 200 = 600 metres

Given speed,  S = 20 m/s

Time taken:

Answer: The train takes 30 seconds to cross the platform.

Tips and Tricks:

1. Identify the 'Distance': The total distance a train needs to cover to cross an object or another train is the sum of their lengths. This is crucial, especially when crossing platforms or another train.

2. Direction Matters: If two trains are moving in opposite directions, their relative speed increases (sum of their speeds). If they move in the same direction, their relative speed is the difference in their speeds.

3. Unit Consistency: Ensure all given units are consistent. Use conversion techniques from Concept 5 if necessary.

4. Use Previous Concepts: Concepts of relative speed, i.e., Concept 6 and Concept 7, are frequently required in train problems. Make sure you're comfortable with those concepts.

5. Shortcut for Stationary Objects: When a train crosses a stationary object (like a pole or a standing person), the distance it covers is equal to its own length.

6. Visual Representation: Draw a simple sketch to understand the problem better, especially if multiple objects or distances are involved.

Problems on trains test a student's ability to quickly and accurately apply concepts of time, speed, and distance, often in combination. As with all TSD problems, practice is essential. Ensure you're familiar with various types of problems and scenarios to tackle them confidently in exams.