Which of the following forces can both attract and repel some objects without touching them?
a. magnetism
b. spring
c. gravity
d. friction

Convection currents are caused by differences in what two things?

Aball is thrown horizontally from a cliff at 8m/s .in what direction is the ball moving 2s later?

Asquare isothermal chip is of width w=5 mm on a side and is mounted in a substrate such that its side and back surfaces are well insulated; the front surface is exposed to the flow of a coolant at tinf=15 °c. from reliability considerations, the chip temperature must not exceed t=85 °c. if the coolant is air and the corresponding convection coefficient is h=200 w/m2 x k, what is the maximum allowable "power" of the chip? if the coolant is a liquid for which h=3000 w/m2 x k, what is the maximum allowable power of the chip?