Speed of train will help us to calculate different types of problems on motion. 1. When a train passes a stationary object: Let x be the length of the train which includes the engine also. When the end of the train passes the object, then the engine of the train has to move a distance equal to the train. Then the time taken by the train to pass the stationary object = length of the train/speed of the train 2. When a train passes a stationary object having some length: When the end of the train passes the stationary object having some length, then the engine of the train has to move a distance equal to the sum of the length of the train and stationary object. Then the time taken by the train to pass the stationary object = (length of the train + length of the stationary object)/speed of the train Problems to calculate the motion or speed of train: 1. Find the time taken by a train 150 m long, running at a speed of 90 km/hr in crossing the pole. Solution: Length of the train = 150m Speed of the train = 90 km/hr = 90 × 5/18 m/sec = 25m/sec Therefore, time taken by the train to cross the pole = 150 m/25m/sec = 6 seconds. 2. A train 340 m long is running at a speed of 45 km/hr. what time will it take to cross a 160 m long tunnel? Solution: Length of the train = 340 m Length of the tunnel = 160m Therefore, length of the train + length of the tunnel = (340 + 160) m = 500m Speed of the train = 45 km/hr Speed of the train = 45 × 5/18 m/sec = 25/2 m/sec = 12.5 m/sec Therefore, time taken by the train to cross the tunnel = 500 m/12.5 m/sec. = 40 seconds. 3. A train is running at a speed of 90 km/hr. if it crosses a pole in just 10 second, what is the length of the train? Solution: Speed of the train = 90 km/hr Speed of the train = 90 × 5/18 m/sec = 25 m/sec Time taken by the train to cross the pole = 10 seconds Therefore, length of the train = 25 m/sec × 10 sec = 250 m 4. A train 280 m long crosses the bridge 170 m in 22.5 seconds. Find the speed of the train in km/hr Solution: Length of the train = 280 m Length of the bridge = 170 m Therefore, length of the train + length of the bridge = 280 m + 170 m = 450 m Time taken by the train to cross the bridge = 22.5 sec = 45/2 sec. Therefore, speed of train = 450 m/22.5 m/sec = 450/45/2 m/sec = 20 m/sec To convert the speed from m/sec to km/hr, multiply by 18/5 Therefore, speed of the train = 20 × 18/5 km/hr = 72 km/hr Speed of Train Relationship between Speed, Distance and Time Conversion of Units of Speed Problems on Calculating Speed Problems on Calculating Distance Problems on Calculating Time Two Objects Move in Same Direction Two Objects Move in Opposite Direction Train Passes a Moving Object in the Same Direction Train Passes a Moving Object in the Opposite Direction Train Passes through a Pole Train Passes through a Bridge Two Trains Passes in the Same Direction Two Trains Passes in the Opposite Direction 8th Grade Math Practice From Speed of Train to HOME PAGE
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