If an equation is dimensionally correct, it does not mean that the equation must be true. On the other hand, when the equation is dimensionally correct, the equation cannot be true. Dimensional analysis is a technique used to check whether a relationship is correct
Explanation :
The forces acting on hot- air balloon are:
Weight, (W)
Force due to air resistance, (F)
Upthrust force, (U)
Its weight W is acting in downward direction. The upthrust force U acts in upward direction. When the balloon is moving upward, the air resistance is in downward and vice versa.
In this case, the hot-air balloon descends vertically at constant speed.
so, 
and 
so,
....................(1)
when it is ascending let the weight that it is releasing is R, so
..........(2)
solving equation (1) and (2)

2F is the weight of material that must be released from the balloon so that it ascends vertically at the same constant speed.
In psychoanalytic therapies, this gives credence and value to an individual's childhood experiences and the unconscious. This would suggest that childhood experiences are highly involve in later life.
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Answer: The correct answer is option (A).
Explanation
Ampacity is defined as the maximum amount of the current carried by the conductor continuously without exceeding its temperature rating.
The ampacity of the wire of the heater is 30 A .And this means that wire is capable of conducting current of maximum amount of 30 Ampere through it without exceeding its temperature rating.
Hence, the correct answer is option is (A).
Answer:
a) 17 km
b) 9 km
Explanation:
The distance is the length of the path.
A to C: 5 km
B to C: 4 km
C to B: 4 km
B to C: 4 km
Total distance = 5 km + 4 km + 4 km + 4 km = 17 km
Displacement is the difference between the starting point and ending point.
Displacement = 9 km − 0 km = 9 km