"Close the door! We aren't heating the outdoors!" is a phrase my father used, especially in the winter. As a matter of fact, all
energy consumption eventually turns into heat, which becomes part of Earth's heat. Wikipedia gives the total energy consumption in 2008 to be 15 TW (15 terawatts = 15 x 1012 W). We can spread this power out over the entire surface area of the Earth to calculate the radiative forcing equivalent of the direct use of energy to be _____ W/m2. The radiating area of the Earth is 4Ï R2, where the radius of the Earth is about 6366 km. (watch your unit conversions).
In absence of friction, total mechanical energy must be conserved.
This means that the change in gravitational potential energy (in magnitude) must be equal to the change in kinetic energy:
As it can be seen, the mass m is on the both sides of the equation, which means that it can be simplified.
We can solve this equation for v (speed at the bottom) as follows:
As it can be seen, the mass has no part in the equation, so, due both are starting from the same height, both people have the same speed at the bottom.
This can be solved using momentum balance, since momentum is conserved, the momentum at point 1 is equal to the momentum of point 2. momentum = mass x velocity m1v1 = m2v2 (0.03kg x 900 m/s ) = 320(v2) v2 = 27 / 320 v2 = 0.084 m/s is the speed of the astronaut
