To solve this problem it is necessary to apply the concepts related to the Period based on gravity and length.
Mathematically this concept can be expressed as

Where,
l = Length
g = Gravitational acceleration
First we will find the period that with the characteristics presented can be given on Mars and then we can find the length of the pendulum at the desired time.
The period on Mars with the given length of 0.99396m and the gravity of the moon (approximately
will be



For the second question posed, it would be to find the length so that the period is 2 seconds, that is:



Therefore, we can observe also that the shorter distance would be the period compared to the first result given.
Answer:
4334.4 J
Explanation:
Work done equals to kinetic energy change
KE=½mv²
Change in KE is given by
∆KE=½m(v²-u²)
Where m is mass of water-skier, KE is kinetic energy, ∆KE is the change in kinetic energy, v is final velocity and u is initial velocity.
Substituting 72 kg for m, 12.1 m/s for v and 5.10 m/s for u then
∆KE=½*72(12.1²-5.10²)=4334.4J
Therefore, the work done by the net external force acting on the skier is equal to 4334.4 J
Questions Diagram is attached below
Answer:

Explanation:
From the question we are told that:
Speed of Train 
Angle 
Height of window 
Width of window 
The Horizontal distance between B and A from Trigonometric Laws is mathematically given by


Therefore
Distance from A-A


Therefore
Time Required to travel trough d is mathematically given as



Answer:
option "c" is correct
Explanation:
Physical science or Physics is the study of matter, energy and their mutual relationship.