<span>The weightlifter does no work. Although he has exerted force, work is the product of force over distance. Since he has not moved the wall he has done no work.</span>
C) alternately increase and decrease
You can find the emf of the battery by using:
Q = CV.
Q = Charge in capacitor plates = 30μC
C = Capacitance of the capacitor = 30μF
V = Q/C = 30/30 = 1V
Ans: The emf of the battery = 1V.
Friction and the applied force are not balanced. The 7 N push is countered by the frictional force of 3 N to push the box with a net force of 4 N.
