Answer: Option (b) is the correct answer.
Explanation:
As Kristina is over training, therefore, there is pain in her muscles because human body also requires rest in order to work or function properly.
That is why, gym trainers suggest to give one day off in a week for your workout sessions so that body muscles should recover.
Thus, we can conclude that if Kristina is over training, then recovery training principle should Kristina consider before continuing her program.
Answer: A) 
Explanation:
The equation for the moment of inertia
of a sphere is:
(1)
Where:
is the moment of inertia of the planet (assumed with the shape of a sphere)
is the mass of the planet
is the radius of the planet
Isolating
from (1):
(2)
Solving:
(3)
Finally:
Therefore, the correct option is A.
The initial volume of the gas is

while its final volume is

so its variation of volume is

The pressure is constant, and it is

Therefore the work done by the gas is

where the negative sign means the work is done by the surrounding on the gas.
The heat energy given to the gas is

And the change in internal energy of the gas can be found by using the first law of thermodynamics:

where the positive sign means the internal energy of the gas has increased.
Answer:
Explanation:
Using the efficiency formula;
Efficiency = Work done by the machine (output)/work done on the machine (input) ×100%
Efficiency =w/50 ×100
90 = 100w/50
Cross multiply
90×50 = 100W
4500 = 100W
W = 4500/100
W = 45Joules
Hence the lever does 45Joules of work on its load
2) Mechanical Advantage= Load/Effort
Given
MA = 4
Load = 500N
4 = 500/Effort
Effort = 500/4
Effort =125N
Hence the effort required to lift the load is 125N