A53 kg person eats a 518 calorie (518 kcal) jelly doughnut for breakfast. (a) how many joules of energy are the equivalent of this jelly doughnut? (b) how many steps must this person climb on a very tall stairway to change the gravita- tional potential energy of the person-earth system by a value equivalent to the food energy in one jelly doughnut? assume the height of a single stair is h = 15 cm. (c) if the human body is only 22% efficient in converting chemical potential energy to mechanical energy, how many steps must the person climb to work off this delicious, amazing breakfast, and how tall of a staircase does this correspond to?

A. 2,168,399.8 J

B. 27832 steps

C. 918.5 m with 6123 steps

Explanation:

A. Since 1 cal equals to 4.1868 joules

B. The change in the gravitational potential energy of the system is given by

Being m the mass of the person, g the gravity constant and z the height difference. The required z is then given by:

Changed to 0.15 m stairs:

C. At 22% efficiency, the values are reduced, since the process is less efficient:

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

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg