Question

A force applied by the engine of a train of mass 2.05*10^6 kg changes it's velocity from 5 ms to 25ms in 5min. The power of the engine is​

Answer 1

Explanation:

Mass of Train=2.05×10^6 kg

final velocity v=25m/s

initial velocity u=5m/s

time taken t=5min = 300s

now acceleration of train a= v-u/t

a= 25-5/300

a=20/300

a=1/15 m/s²

so force applied by the engine F=ma

F= 2.05×10^6 × 1/15

F= 1.3×10^5 N

now here we are talking about average power..

so average power is equal to work done per unit time...

so P=W/t

work done =F.s. (s is displacement of train)

to find s apply 2nd equation of motion

s=ut+1/2at²

s=5×300+1/30×300×300

s=1500+3000

s=4500m

so work done

W=F.s

W=1.3×10^5×4500

now average power

P=W/t

P=13×45×10^6/300

P=195×10^4

P=1.95×10^6 watt

hope you got your answer