We want to find the rate of heat transfer from a horizontal and flat piece of ground, of size 20 m by 20 m surrounded by a fence. the ground temperature is 33 c, while the air above is 22 c and still. there is a natural convection set up. for air at these temperatures, we can approximate pr- 0.7 (as usual), k ·0.030 w/m-c and the kinematic viscosity v. 21x10-6m2/s what is the rate of heat transfer from this ground? note: if your grashof number exceeds the limits in table 8-3, our best estimate comes from using the right configuration, and just using the higher number. a)- 450 w b)-7500w c)-8.6 w d)-918 w e)- 2600 w

If two metal balls each have a charge of -10^-6 c and the repulsive force between them is 1 n, how far apart are they? (coulomb's constant is k = 9.0x 10^9 n-m^2/c^2? 9.5 m 9.0 mm 9.5 cm 0.9 m .

Mass (kg) force (n) 5 25 10 50 15 75 20 100 a student was trying to find the relationship between mass and force. he placed four different masses on a table and pulled them using a spring scale. the table shows the different masses used in the experiment and the force required to pull each mass. the student concluded that more force was required to pull heavier objects. what comment would you make regarding his conclusion? a) no clear relation can be observed between mass and force from the data. b) there is a direct proportion between the mass and force listed in the table. c) gravity should have been taken into account while performing the experiment. d) there is an inverse proportion between the mass and force listed in the table.

What is required for an electric charge to flow through a wire? zero resistance in the wire a balance of electric potential high resistance in the wire a difference in electric potential