1. Four point charges are arrangened in a line at the distances shown below. Charges A, B,C,D have magnetitudes of +9, -5C, -12C, respectively. A negative test charge is placed at point C.

A---------25cm-----B--------25cm----C-----25cm-----D.

What is the magnitude of the force acting on the test charge?. (K is Coulomb's constant, Z is the magnitude of the test charge in coulombs).

The answer is 236 kZ newtons

How we solve it?.

2.

A solid weights 60 ibs in air. To determine its density it is immersed in a test liquid of weight-density 10ibs/ft^3. If the solid weight 40 Ibs when immersed inthe liquid, its density is closest to :

The answer is 1 slug/ft^3.

how we solve it/.