Question

a train is 100m long is moving with uniform velocity of 45km/h.the time it will cross a bridge 1km long is

Answer 1

Answer:

The formula for velocity is distance ÷ time taken. In symbols:

V=S÷t.

Where:

V = velocity

S = distance

t = time taken.

To solve your question:

You need to convert each unit to its standard form, so:

V = 45Km/hr = 12.5m/s

S = 1km = 1000m

t = ?

Solution

V = S÷t

12.5 = 1000÷t

Making t subject of formula:

t = 1000÷ 12.5

t = 80 seconds.

So it will take 80 seconds for a train moving at 12.5 meters every second to cross a kilometer long bridge.

However,

The question states the train is 100 meters long.

This means the last point on the train has an extra 100 meters to cover.

So it becomes:

t = 1100 ÷12.5

t = 88 seconds.

So the time it takes a train 100m long, moving at 12.5km/hr to cover 1km is 88 seconds or 1 minute, 28 seconds.

Answer 2

Answer:

$\bigstar{\bold{Time=88\:s}}$

Explanation:

$\Large{\underline{\underline{\bf{Given:}}}}$

• Length of train = 100 m
• Length of bridge = 1 km = 1000 m
• Speed = 45 km/hr = 12.5 m/s

$\Large{\underline{\underline{\bf{To\:Find:}}}}$

• Time taken to cross the bridge

$\Large{\underline{\underline{\bf{Solution:}}}}$

→ Total distance = Length of train + Length of bridge

   Total distance = 100 + 1000

   Total distance = 1100 m

→ Time taken is given by the equation

   Time = Distance / Speed

→ Substituting the given datas we get,

   Time = 1100/12.5

   Time = 88 s

$\boxed{\bold{Time=88\:s}}$

$\Large{\underline{\underline{\bf{Notes:}}}}$

→ Speed is given by the equation

  Speed = Distance/Time

→ Speed is a scalar quatity. It's unit is m/s.