Answer:
The boat's velocity relative to Earth is 3.91 m/s.
Explanation:
Given;
speed of ferry due north,
= 2.5 m/s
speed of the river to the east,
= 3.0 m/s
The boat's velocity relative to Earth is given by;

Therefore, the boat's velocity relative to Earth is 3.91 m/s.
Its mass, I suppose. Unless the balloon explodes.
Answer:

Explanation:
Given the parallex of the star is 0.1 sec.
The distance is inversely related with the parallex of the star. Mathematically,

Here, d is the distance to a star which is measured in parsecs, and P is the parallex which is measured in arc seconds.
Now,

And also know that,

Therefore the distance of the star is
away.
Answer:
0.08
Explanation:
this problem assume that both of whale and submarine are in rest position or in constant linier motion in same direction and same speed.
The sound will travel from Submarine to the whale and back again to submarine. so the time will be like this
t = 2d/v
t = 2*58.8/1520
t = 117.6/1520
t = 0.077368 s
t ≈ 0.08 s (less then 1 s)
Answer:
Mechanical energy is the ordered movement of the molecules as a single unit. Thermal energy is the random movement of the molecules. Mechanical energy can be 100% converted to thermal energy, but thermal energy cannot be fully converted to mechanical energy.