A real question, one with a question mark?
Answer:
Option (C) is correct.
Explanation:
Assuming that the hiker starts walking from the origin O as shown in the figure.
First, he walks 200 m west to point A (say), then he walks 100 m north to the final point B (say) as shown in the figure.
The final point B is in the north-west direction, therefore, the resulting point is in the north-west direction.
Hence, option (C) is correct.
Answer:

Explanation:
Given that,
Initial speed, u = 0
Final speed, v = 40 m/s
Time, t = 2 s
We need to find the acceleration of the aircraft. We know that, acceleration is equal to the rate of change of velocity. So,

So, the acceleration of the aircraft is
.
Answer:

Explanation:
For n-=1 state hydrogen energy level is split into three componets in the presence of external magnetic field. The energies are,
,
,

Here, E is the energy in the absence of electric field.
And
are the highest and the lowest energies.
The difference of these energies

is known as Bohr's magneton.
B=2.5 T,
Therefore,

Now,

Therefore, the energy difference between highest and lowest energy levels in presence of magnetic field is 
Answer:
KE = 100 J
Explanation: Should be correct