*Urgent* (Part 1)

A merry-go-round rotates at the rate of 0.4 rev/s with an 99 kg man standing at a point 2.5 m from the axis of rotation. What is the new angular speed when the man walks to a point 1 m from the center? Consider the merry-go-round is a solid 73 kg cylinder of radius of 2.5 m. Answer in units of rad/s.

(Part 2)

What is the change in kinetic energy due to this movement? Answer in units of J.

6.5 rad/s

11.695 kJ

Explanation:

Using the principle of conservation of momentum, we have

L1 = L2 and

I1w1 = I2w2, with I being the moment of inertia and w being the angular velocity.

w1 = 0.4 rev/s = 0.4 * 2π = 2.51 rad/s

Moment of Inertia, I = ½MR² + mr²

I1 = ½ * 73 * 2.5² +99 * 2.5²

I1 = 73 * 3.125 + 99 * 6.25

I1 = 228.125 + 618.75

I1 = 846.875 kgm²

The man has been said to have walked 1 m away from his position, so then

I2 = ½ * 73 * 2.5² + 99 * 1²

I2 = 228.125 + 99

I2 = 327.125 kgm²

From the formula stated above,

w2 = I1w1 / I2

w2 = (846.875 * 2.51) / 327.125

w2 = 2125.65725 / 327.125 rad/s

w2 = 6.5 rad/s

2

K = Iw²

K = 846.875 * 2.51²

K = 2125.65725 J

K'= Iw²

K' = 327.125 * 6.5²

K' = 13821.03125 J

Change in energy is given as, K' - K, so that

Energy, E = 13821.03125 - 2125.65725

Energy, E = 11.695 kJ

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