Applying force all the time is bad for you body, the object, and the environment and how it looks at you. First of all, you could strain, break, fracture, you name it, to your bones and muscles. Second of all, you could manage to break that object, not even move it. For example, say you have to move a heavy object to save the town from almost flooding and you strain or break your arm. To society or the people watching you do this, you look like a wimp or you're not strong. Then you have a bad reputation in the people's eyes and you get picked on or bullied because of that. You don't have move that object. You could find a way to work around the object and get simpler ways that only you thought of at the time.
No they all don't need a medium to travel.
Example is electromagnetic waves which travel through vacuum.
Answer:
(a) The x-component of velocity is 31.55 km/h
(b) The y-component of velocity is 44.92 km/hr
Solution:
As per the solution:
The relative position of ship A relative to ship B is 4.2 km north and 2.7 km east.
Velocity of ship A, 
= 22 km/h towards South = 
Velocity of ship B, 
= 39 km/h Towards North east at an angle of 
= 
Now, the velocity of ship A relative to ship B:
Now,
Assuming there is no force of friction...
F = ma
F = (1300kg)(1.5m/s^2)
F = 1950N
Just multiply mass by acceleration.
1300 x 1.5 = 1950N.
