There are two external force acts on the chair.
1. The force due to earth gravity, acts in the downward direction.
2. Reaction force of the gravity, which acts in the Upward direction (Normal Force).
On every object, there is a force acts due to gravity of earth, which pulls the object towards the centre of earth, known as gravity force, always acts in the downward direction. Mathematically it's given as
F=mg
here, m is the mass of the object, and g is the acceleration of gravity.
To balance this gravity force, a counter force acts in the opposite direction, whose magnitude is equal to the force of gravity
Eric is writing about the cell wall.
Chloroplast is for photosynthesis.
Mitochondria releases energy from respiration.
Nucleus controls the activities of the cell.
But the cell wall supports and gives structure to the cell.
Answer:
Ratio of magnetic field will be 
Explanation:
We have given radius of the loop r = 30 mm = 0.03 m
We know that magnetic field at the center of the loop is given by
---------eqn 1
Number of turns in the solenoid is given as n = 3 turn per mm = 3000 turn per meter
We know that magnetic field due to solenoid is given by
-------------eqn 2
Now dividing eqn 1 by eqn 2

Answer:
Remains same
Explanation:
= Time period of oscillation
= mass
= spring constant
Time period of oscillation is given as

we know that as we move from earth to moon, the value of spring constant "k" and mass "m" remains unchanged because they do not depend on the acceleration due to gravity.
Time period depends on spring constant inversely and directly on the mass.
hence the time period remains the same.