Train M leaves Meerut at 5 A.M. and reaches Delhi at 9 A.M. Another train leaves Delhi at 7 A.M. and reaches Meerut at 10.30 A.M. At what time do the two trains cross each other?
Time taken by train M from Meerut to Delhi = 4 hoursIt travels for 2 hours before train D starts.Time taken by train D from Delhi to Meerut = 3.5 hoursLet distance between Delhi & Meerut = LCM(4,3.5) = 28 kmsSpeed of Train M = 28/4 = 7 kmphSpeed of Train D = 28/3.5 = 8 kmphTrain M covers 7 x 2 = 14 km by the time Train D starts at 7 AM.So, distance between the two trains at 7 AM is 28 - 14 = 14kmRelative speed = 7 + 8 = 15 kmphTime taken to cross each other = 14/15 hours or 56 minutes.=> They meet at 7:56 AM.Note :Distance = Speed x TimeRelative Speed = Sum of individual speeds when two objects move in opposite directions.:-)
How can I find average speed if a boy walks to his school at a distance of 6 km with a speed of 2.5 km/h and walks back with a constant speed 5km/hr?
This question is very simple.Average speed = Total Distance / Total Time TakenWe have given speeds S1 and S2S1 = 2.5 km/hrS2 = 5 km/hrAnd Distance D1 and D2D1 = 6 kmD2 = 6 kmTotal Distance = D1 + D2 = 6 + 6 = 12 kmNowT1 = D1/S1T1 = 6/2.5 = 2.4 hrT2 = D2/S2T2 = 6/5 = 1.2 hrTotal Time = T1 + T2 = 2.4 + 1.2 = 3.6 hrNowAverage Speed = Total Distance / Total Time = 12 / 3.6Average Speed = 3.33 km/hr
Is there an easy way to memorize first 20 elements of Periodic Table of the Elements?
You can use mnemonics and make a simple periodic table, there you can assign atomic number and their atomic weight will be more or less twice the atomic number... Its just a case of familliarization..
Physics question plz help?
An airplane propeller is 2.18 m in length (from tip to tip) and has a mass of 127 kg . When the airplane's engine is first started, it applies a constant torque of 1890 N⋅m to the propeller, which starts from rest. What is the angular acceleration of the propeller? Treat the propeller as a slender rod. What is the propeller's angular speed after making 5.00 rev ?