Question

A train starts from rest and accelerates uniformly for 20 s to attain a velocity of
90 km/h. It travels at constant velocity for 15 minutes. The driver applies brakes
to stop the train in next 5 s. Find the total displacement of the train.​

Answer 1

Answer:

Given that,

Acceleration a=−0.5m/s  

2

 

Speed v=90km/h=25m/s

Using equation of motion,  

v=u+at

Where,  

v = final velocity

u = initial velocity

a = acceleration

t = time

Put the value into the equation

Finally train will be rest so, final velocity,v=0

0=25−0.5t

25=0.5t

t=  

0.5

25

​  

 

t=50 sec

Again, using equation of motion,  

S=ut+  

2

1

​  

at  

2

 

Where, s = distance

v = final velocity

u = initial velocity

a = acceleration

t = time

Put the value into the equation

Where S is distance travelled before stop

s=25×50−  

2

1

​  

×0.5×(50)  

2 s=625 m

Explanation: