Microwave<span> ovens are so quick and efficient because they channel </span>heat<span> energy directly to the molecules (tiny particles) inside </span>food<span>. </span>Microwaves heat food<span> like the sun heats your face—by radiation. A </span>microwave<span> is much like the electromagnetic waves that zap through the air from TV and radio transmitters</span>
We know that by Hooke's Law,
F = kx; where F is the net force on the spring, k is the spring constant and x is the extension.
We are told that all the springs have the same spring constant as the first, so we first calculate its spring constant.
F = ma = 4.1 × 9.81
= 40.2 Newtons
k = 40.2 ÷ 0.13
k = 309 Newtons / m
Now, for the spring under consideration, the mass is
m2 = 12.3 kg
The net force will be the difference of the downward force of the mass's weight and the upward force of the elevator. Thus,
F = 12.3 × 9.81 - 12.3 × 4.2
F = 69 Newtons
x = 69 ÷ 309
x = 0.22 m = 22 cm
Answer:1) 100 gm mass should be placed at 95 cm mark.
2) Mass of 112.5 gm should be placed at 90 cm mark.
Explanation:
For equilibrium of the meter stick the sum of the moment's generated by the masses should be equal and opposite
Answer to part b)
Since a meter stick is 100 cm long and it is pivoted at it's center i.e at 50 cm
Thus
1) Moment generated by 100 gm mass about center = 
Let a mass 'm' be placed at 90 cm mark thus moment it generates equals

Equating both the moments we get

Answer to part a)
Let the 100 grams weight be placed at a distance 'x' right of center
Moment generated by 100 grams weight equals

equating the moments of the forces we get


thus the mass of 100 gm should be placed at 95 cm mark in the scale.
Im pretty sure the answer if elasticity