A child of mass 40.0 kg is in a roller coaster car that travels in a loop of radius 8.80 m. At point A the speed of the car is 14.2 m/s, and at point B, the speed is 15.0 m/s. Assume the child is not holding on and does not wear a seat belt.
a. What is the force (in N) of the car seat on the child at point A?
b. What is the force (in N) of the car seat on the child at point B?
c. What minimum speed (in m/s) is required to keep the child in his seat at point A?

compass can be used day and night, cloudy or sunny

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