Which of the following is an example of the electrostatic force acting in an atom?
a. an electron repelling a proton
b. a proton repelling another proton
c. a neutron repelling an electron
d. a neutron repelling another neutron

Which simple machine is not part of this compound machine? a. lever b. pulley c. inclined plane d. wheel and axle

World class speed skaters can skate a 3,000-m course in about 4 minutes.what is their average speed for this course? a. 12.5 m/sb. 1.33 m/sc. 1.25 m/sd. 13.3 m/s

Two forces produce equal torques on a door about the door hinge. the first force is applied at the midpoint of the door; the second force is applied at the doorknob. both forces are applied perpendicular to the door. which force has a greater magnitude?