Question

A car of length 4.3m is travelling at 105kn/h it passes over a bridge of length 36m Calculate the time in seconds it takes to pass over the bridge completely​

Answer 1

Car takes 1.53 seconds to pass over the bridge completely​

Solution:

Given that car of length 4.3m is travelling at 105km/h it passes over a bridge of length 36m

To find: time in seconds car takes to pass over the bridge completely​

From given information,

Speed of car = 105 km/hr

Let us convert the kilometer per hour to meter per second

To convert km/hr into m/sec, multiply the number by 5 and then divide it by 18

$\rightarrow 105 \frac{km}{hr} = 105 \times \frac{5}{18} \frac{m}{sec} = 29.167 m/sec$

So speed of car = 29.167 m/sec

Length of car = 4.3 m

Length of bridge = 36 m

For the car to completely pass the bridge, back end of car should cross the endpoint of bridge

So the distance covered by car to pass over the bridge completely​ = 4.3 + 36 + 4.3 = 44.6 m

Time taken is given as:

$time = \frac{distance}{\text{ speed of car }}$

$time = \frac{44.6}{29.167} = 1.529 \approx 1.53$

So car takes 1.53 seconds to pass over the bridge completely​