Question

A boat starts to move upstream from rest with an acceleration of 2.5 m/s2

for

10 s before its engine is shut off.

a) How long will it take for the boat to start moving downstream once the engine is shut,

if the stream is flowing down with an acceleration of 2 m/s2

.

b) How much distance will the boat cover before it attains a velocity of 10 m/s while

going down?

Pls answer me if u know the crct answer​

Answer 1

Answer:

A. 12.5 s

B. 25 m

Explanation.

When the boat starts to move upstream,

u = 0 m/s

a = 2.5 m/s²

t = 10 s

a. When the engine gets shut off, immediately the acceleration towards the upstream will also be stopped and thus, downward acceleration will begin.

Before shutting down, the boat would have a velocity of = v = u+at

= v = at

= v = 2.5*10

= v = 25 m/s

Now, the engine is shut off, so retardation at a rate of 2 m/s² will begin.

u = 25 m/s

a = -2 m/s²

v = 0 m/s

= v = u-at

= 0 = 25-2t

= 2t = 25

= t = 12.5 s

At 12.5 s the boat will come to rest again and will start to go downstream.

b. u = 0 m/s

v = 10 m/s

a = 2 m/s²

v² = u²+2aS

v²-u² = 2aS

(v²-u²)/2a = S

(10²)/2*2 = S

100/4 m = S

= 25 m = Distance Covered

Hope this helps.