Answer:
20 J
Explanation:
The law of conservation of energy states that (if we neglect air resistance) the mechanical energy of an object in free fall is conserved:
where
E is the mechanical energy, which is the sum of
U = potential energy
K = kinetic energy
When the ball is held 10 meters above the ground, its gravitational potential enegy is U = 20 J, while its kinetic energy is K = 0 (because the ball is at rest). Therefore, its mechanical energy is
E = U + K = 20 J + 0 = 20 J
Just before hitting the ground, its potential energy is zero (because its height is now zero), and since the mechanical energy must be conserved, we still have that E = 20 J. So, we can find the kinetic energy just before hitting the ground:
Construction, like building a home/building, digging, like in a mine, and opening a soda can, where the part to open is a lever.
Answer:
75.6J
Explanation:
Hi!
To solve this problem we must use the first law of thermodynamics that states that the heat required to heat the air is the difference between the energy levels of the air when it enters and when it leaves the body,
Given the above we have the following equation.
Q=(m)(h2)-(m)(h1)
where
m=mass=1.3×10−3kg.
h2= entalpy at 37C
h1= entalpy at -20C
Q=m(h2-h1)
remember that the enthalpy differences for the air can approximate the specific heat multiplied by the temperature difference
Q=mCp(T2-T1)
Cp= specific heat of air = 1020 J/kg⋅K
Q=(1.3×10−3)(1020)(37-(-20))=75.6J