Question

Annabelle's taking the Polar Express all the way to the North Pole The Polar Express is 100 m long and it takes 30 seconds to cross and his 400m rice Bridge what speed is the train going at

Answer 1

Given that the length of the train is 100 m when the train covers the 400 m of the bridge; the length o the train, 100 m, is still on the bridge. The actual distance that the train covers to cross the bridge is 400 m (the length of the bridge) plus 100 m (the length of the train), which is equal to 500 m.
Now,
`500m( (1km)/(1000m) )= (1)/(2) km`, and
`30s( (1h)/(3600s) )= (1)/(120) h`

We know that
`d=vt`, so
`v= (d)/(t)`.And for our previous calculation we also know that
`d= (1)/(2) km` and
`t= (1)/(120) km`. The only thing left is replacing those values in our equation:


`v= ( (1)/(2)km )/( (1)/(120) h)`

`v= (120km)/(2h)`

`v=60kmh`

We can conclude that the speed of the train is 60 kmh.

Answer 2

Total distance is calculated by taking summation of Polar express and the rice bridge. So Total distance is 500 m which is 0.5 Km. Time is 30 sec which when converts to hours= 30/3600= 0.0083 hrs. So Speed= Distnace/ Time = 0.5/0.0083 =60.2km/hr Hence in this case the speed of train is calculated to be 60.2 Km/hr.