Answer:
The speed of the wind is 25 km/hr.
Explanation:
Let us call
the speed of the plane and
the speed of the wind. When the plane is flying against the wind, it covers the distance of 900-km in 2 hours (120 minutes); therefore;
(1). 
And when the plane is flying with the wind, it covers the same distance in 1 hour 48 minutes (108 minutes)
(2). 
From equation (1) we solve for
and get:
,
and by putting this into equation (2) we get:





or in km/hr this is

Answer:
reduce the velocity of collision
Yes spoon can sound like a bell. To prove this, we perform an experiment.The handle of the spoon is tied at the mid point of the string, then wrap the ends of the string around pointer fingers. Now place fingers in ears. Lean over so that spoon hangs freely and swing the spoon so it taps against a door.
A sound is produced because the spoon vibrated, causing sound waves to travel up the string and into ears.
The answer would be the sound waves.
Here it is an application of Newton's III law
as we know by Newton's III law that every action has equal and opposite reaction
So here as we know that two boys jumps off the boat with different forces
from front side of the boat the boy jumps off with force 45 N which means as per Newton's III law if boy has a force of 45 N in forward direction then he must apply a reaction force on the boat in reverse direction of same magnitude
So boat must have an opposite force on front end with magnitude 45 N
Now similar way we can say
from back side of the boat the boy jumps off with force 60 N which means as per Newton's III law if boy has a force of 60 N in backward direction then he must apply a reaction force on the boat in reverse direction of same magnitude
So boat must have an opposite force on front end with magnitude 60 N
So here net force due to both jump on the boat is given by



so boat will have net force F = 15 N in forward direction due to both jumps