A spiral spring of natural length 20.00cm has a scale pan hanging on its lower end while the other end is
fixed firmly to a support. When an object of mass 50g
is placed in the pan, the length of the spring becomes
22.00 cm. When another object of mass 70g is placed in
The pan, the length becomes 22.25cm Calculate the
mass of the scale pan. (g = 10m/s]

The  mass of the scale pan : 0.11 kg

Given

A spiral spring's length = 20 cm

mass 50 g ⇒ the length = 22 cm

mass 70 g ⇒ the length = 22.25 cm

Required

the  mass of the scale pan

Solution

Hooke's Law :

The spring constant (k) :

mass of the scale pan=m(for 50 g mass) :

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia