Answer:
6.15 s
Explanation:
The period of a simple pendulum is given by the equation

where
L is the length of the pendulum
g is the acceleration of gravity
For the pendulum in this problem,
L = 1.5 m (length)
(acceleration due to gravity on Earth)
Therefore, its period is

And therefore, the time taken for the pendulum to complete 2.5 oscillations is equal to 2.5 times the period:

This question is a bit ambiguous because all parts of a scientific argument must be supported by valid data. However, among the choices, the closest synonym to "valid data" would be evidence. Evidence is the body of facts or information that support a given idea.
I think that the answer is A
In order to calculate the unknown reaction force, we need to know that the sum of forces pointing down is equal the sum of the forces pointing up, so all forces will be in equilibrium.
So we have: