The engine of a locomotive exerts a constant force of 8.1*10^5 n to accelerate a train to 68 km/h. determine the time (in min) taken for the train of mass 1.9*10^7 kg to reach this speed from rest.

443.1 s

Explanation:

Given

Engine of a locomotive exerts a force of

Mass of train

Final speed (v)

F=ma

so

and acceleration is

Explanation:

It is given that,

Force acting on the engine,

Initial speed of the engine, u = 0 (at rest)

Final speed of the engine, v = 68 km/h = 18.88 m/s

Mass of the train,

We need to find the time taken by the train. Firstly, we will find the acceleration of the engine from Newton's second law of motion as :

Now using first equation of motion to find time taken as :

t = 449.52 seconds

or

t = 7.49 minutes

So, the time taken for the train to reach this speed is 7.49 minutes. Hence, this is the required solution.

second mirror gathers light from a faraway object and reflects it to another mirror. - a.

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day