One of the components that affect the period is gravity (the other is length). This gravity is basically the value of the effective acceleration that acts on the body due to gravity. When the elevator is over free fall, the effective gravity becomes zero. Mathematically this can be visualized as,

Since this value is zero, the period would tend to be infinite,

Therefore the frequency that is inversely proportional to the period would be defined as



In this way there is no frequency on the body which will not generate any oscillation on the body
The answer to this question is true
Answer: 100 N
Explanation: Taking into account the second Newton Law the total force applied to any system is equal to the mass *acceleration.In this case the crate moves at constant speed so the accelaration is zero. In order to satisfy this fact, the friction force must be equal the applied force of 100 N .
It depends on what is the reference frame where the velocity of the leaf (6 m/s) is measured.
If it is measured with respect to the creek, then the answer is simply "6 m/s south".
If it is measured with respect to the observer moving toward the leaf, then the velocity of the leaf relative to the ground is actually the sum between the velocity of the leaf relative to the observer (6 m/s south, so 6 m/s) and the velocity of the observer relative to the ground (2 m/s north, so -2 m/s):

and the direction is south.
Entirely horizontal.
An object will continue to travel with the same velocity unless an external force is applied.
There are no external forces acting in the horizontal direction (except air resistance but the is negligable) so the ball will move in the horizonontal direction with with same speed at all times.
Force of gravity is acting downwards, meaning it is constantly acelleraring at 9.8ms^-2 towards the ground. When the ball reaches its heighest point, it is where the ball has stopped moving up and starts to move down, therfore it is not moving vertically at all.