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A train moving at the rate of 72 kmph crosses a pole in 20 seconds. How much time will the train require to cross car moving at speed of 18 kmph in opposite direction?
Correct answer is '16 sec'. Can you explain this answer?
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Most Upvoted Answer
A train moving at the rate of 72 kmph crosses a pole in 20 seconds. H...
Given:
- Speed of train = 72 km/h
- Time taken to cross a pole = 20 seconds
To find:
- Time taken to cross a car moving at a speed of 18 km/h in the opposite direction
Explanation:
To solve this problem, we can use the concept of relative speed.
Step 1: Find the actual speed of the train
Since the train crosses a pole in 20 seconds, we can find the actual speed of the train using the formula:
Speed = Distance/Time
Distance = Speed * Time
Distance = 72 km/h * 20 seconds
Distance = 1440 meters
Step 2: Find the relative speed
The relative speed of two objects moving in opposite directions is the sum of their individual speeds.
Relative Speed = Speed of train + Speed of car
Relative Speed = 72 km/h + 18 km/h
Relative Speed = 90 km/h
Step 3: Find the time taken to cross the car
To find the time taken to cross the car, we can use the formula:
Time = Distance/Speed
Distance = 1440 meters (as calculated in Step 1)
Speed = Relative Speed = 90 km/h
Converting the speed from km/h to m/s:
Speed = 90 km/h * (1000 meters/1 km) * (1 hour/3600 seconds)
Speed = 25 m/s
Time = Distance/Speed
Time = 1440 meters/25 m/s
Time = 57.6 seconds
Step 4: Convert the time to seconds
Since the time is given in seconds, we need to convert it from seconds to minutes.
1 minute = 60 seconds
57.6 seconds = 57.6/60 minutes
57.6 seconds = 0.96 minutes
The time taken to cross the car is approximately 0.96 minutes or 57.6 seconds.
Conclusion:
The train will require approximately 57.6 seconds to cross a car moving at a speed of 18 km/h in the opposite direction.
- Speed of train = 72 km/h
- Time taken to cross a pole = 20 seconds
To find:
- Time taken to cross a car moving at a speed of 18 km/h in the opposite direction
Explanation:
To solve this problem, we can use the concept of relative speed.
Step 1: Find the actual speed of the train
Since the train crosses a pole in 20 seconds, we can find the actual speed of the train using the formula:
Speed = Distance/Time
Distance = Speed * Time
Distance = 72 km/h * 20 seconds
Distance = 1440 meters
Step 2: Find the relative speed
The relative speed of two objects moving in opposite directions is the sum of their individual speeds.
Relative Speed = Speed of train + Speed of car
Relative Speed = 72 km/h + 18 km/h
Relative Speed = 90 km/h
Step 3: Find the time taken to cross the car
To find the time taken to cross the car, we can use the formula:
Time = Distance/Speed
Distance = 1440 meters (as calculated in Step 1)
Speed = Relative Speed = 90 km/h
Converting the speed from km/h to m/s:
Speed = 90 km/h * (1000 meters/1 km) * (1 hour/3600 seconds)
Speed = 25 m/s
Time = Distance/Speed
Time = 1440 meters/25 m/s
Time = 57.6 seconds
Step 4: Convert the time to seconds
Since the time is given in seconds, we need to convert it from seconds to minutes.
1 minute = 60 seconds
57.6 seconds = 57.6/60 minutes
57.6 seconds = 0.96 minutes
The time taken to cross the car is approximately 0.96 minutes or 57.6 seconds.
Conclusion:
The train will require approximately 57.6 seconds to cross a car moving at a speed of 18 km/h in the opposite direction.
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Community Answer
A train moving at the rate of 72 kmph crosses a pole in 20 seconds. H...
Given
Speed of train = 72 kmph
Time = 20 seconds
Speed of car = 18 kmph
Formula used:
Speed = Distance / Time
1 kmph = 5 / 18 m/s
Calculating length of train
⇒ 72 kmph = 72 × 5 / 18 m/s
⇒ Speed of train = 20 m/s
⇒ length of train = Speed × Time
⇒ length = 20 × 20
⇒ Length of train = 400 m
Now, calculate relative speed
⇒ car is moving in opposite direction as train hence relative speed = 72 + 18
⇒ Relative speed = 90 kmph
⇒ Relative speed = 25 m/s
⇒ Time taken to cross car = 400/25
⇒ Time taken = 16 seconds
∴ Train takes 16 seconds to cross the car
Hence, the correct answer is 16 sec.
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A train moving at the rate of 72 kmph crosses a pole in 20 seconds. How much time will the train require to cross car moving at speed of 18 kmph in opposite direction?Correct answer is '16 sec'. Can you explain this answer?
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