Question

carefree express is 200m long and is running at a rate of 54kmph it will cross a bridge 55m long in​

Answer 1

Answer:

speed=54*5/18=15m/s

time=255/15=17sec

Answer 2

Carefree Express takes 17 seconds to cross the bridge.

Step-by-step Explanation:
Given:
Length of train = $d_{1}$ = 200m

Length of bridge = $d_{2}$ = 55m

Speed of train = $v$ = 54kmph

Formulas Used:

$v\hspace =\frac{d}{t}$

Here, $v$ is the speed of a body (here, it is Carefree Express)

         $d$ represents the distance traveled

         $t$ represents the time taken to travel the distance

From this formula, we can also write

$t = \frac{d}{v}$

This can be used to give the time needed by a body (here Carefree Express) to travel $d$ distance at a speed of $v$.

Concept Used:

For a long body like a bridge, the distance covered by the train to cross will be the sum of its length and the bridge length.

For a stationary, thin body like a lamp post or a human, the train has to cover a distance equal to its length to cross it.

Steps:

• Since the bridge is a long object, total distance covered = $d$ = length of train + length of the bridge
• So, total distance = $d = d_{1}+ d_2=200+55=255m$
• Speed of train = 54 kmph.
• We need to convert the speed into meters per second. So,
  $54 kmph = \frac{54*1000}{60*60}m/s$
• Solving this, we get speed = $v = 15 m/s$
• Hence, the time taken to cross the bridge can be given by $t = \frac{d}{v}$
• Substituting the values in the formula, we get
  $t = \frac{255}{15}$
• Solving this, we get $t = 17s$
  So, time required to cross the bridge is 17 seconds.