In a spring gun, a spring of mass 0.240 kg and force constant 3100 N/m is compressed 2.00 cm from its unstretched length. When the trigger is pulled, the spring pushes horizontally on a 5.5×10−2 kg ball. The work done by friction is negligible. Calculate the ball's speed when the spring reaches its uncompressed length ignoring the mass of the spring.

The ball's speed when it reaches its uncompressed length = 0.73m/s

Explanation:

The speed of the ball is greatest when acceleration is zero and the net force on the ball is zero.

Given:

Force constant = 3100Nm

Compressed length =2.0cm= 0.02m

Spring mass= 0.240kg

Mass of barrel = 5.5 ×10^-2kg

Resistant force,F = ma

F= 5.5×10^-2 × 9.8 = 0.539N

0.538/3100 = 1.738×10^-4m

Initial force on the ball = (3100× 0.02) - 0.539

Initial force on ball = 62 - 0.539 = 61.46N

Final net force on ball= 0N

Mean net force of ball = 1/2 (61.46 +0) = 30.73N

Net on ball = 30.73 ×(1.74×10^-4) = 5.35×10^-3J

Transfer to KE = 1/2mv^2

V^2 = (5.35×10^-3)/0.01

V^2=0.535

V = Sqrt(0.535)

Vmax= 0.73m/s

because growing process had stoped after 4-5 year

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