Currently, recreational balloons are not filled with hydrogen or helium but with hot air; the pilot has a small propane burner to heat the air in the balloon. If the balloon is a sphere 20 m in diameter, and if the total weight of the balloon, pilot, passenger compartment, propane burner, propane tank, ropes, etc is 200 kg, what average temperature must the air in the balloon have to just barely lift the balloon

Abox is pushed down at an angle of 32 degrees on a rough surface. the box moves to the right.what equation should be used to find the net force in the y-direction? answers: a. fnet,y = fn - fgb. fnet,y= fp - ffc. fnet,y = fn-fg- fpcos(32)d. fnet,y = fn-fg-fpsin(32)

A23 kg log of wood begins from rest, 300 m up a sluice (a water track used to transport logs, think of it as an inclined plane with negligible friction) inclined at 20° to the horizontal. after it reaches the flat waterway at the bottom it collides elastically with a 100 kg block of wood initially at rest near the base of the incline. (a) how long does it take the 23 kg log to travel down the incline? (b) what is the speed of the 23 kg log at the bottom of the incline? (c) what are the velocities of both blocks of wood after the collision? (d) what is the total kinetic energy before the collision? (e) what is the kinetic energy of the 23 kg log after the collision? (f) what is the kinetic energy of the 100 kg block of wood after the collision? (g) what is the total kinetic energy after the collision? (h) compare the total initial and total final kinetic energies. is this consistent with what you would expect for elastic collisions? explain!

In a given chemical reaction, the energy of the products is greater than the energy of the reactants. which statement is true for this reaction?