A boat travels upstream and after one hour has gone 10 km. the boat next travels downstream and after one hour has gone 18km. if the boats speed relative to the water is constant, what is the speed of the river

4 km/h

Explanation:

Let the boat's speed relative to the water be u and the speed of the water be v (both in km/h)

upstream: boat's speed = u - v

during t = 1 hour, the distance is (u - v) * 1 = 10            (1)

downstream: boat's speed = u + v

during t = 1 hour, the distance is (u + v) * 1 = 18          (2)

(2) - (1): 2v = 18 - 10 = 8, so v = 4 km/h

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2

another example of kinetic energy would be,

kinetic energy   >     moving energy

answer   >   letter choice (c),   a hammer falling off a table.

hope that !                                         : )