This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 26.16. Model: Charges A, B, and C are point charges. Visualize: Please refer to Figure EX26.16. Charge A experiences an electric force B on A F r due to charge B and an electric force C on A F r due to charge C. The force B on A F r is directed to the right and the force C on A F r is directed to the left. Solve: Coulomb’s law yields: ( 29 ( 29 ( 29 ( 29 9 2 2 9 9 5 B on A 2 2 9.0 10 N m /C 1.0 10 C 1.0 10 C 9.0 10 N 1.0 10 m F × × × = = × × ( 29 ( 29 ( 29 ( 29 9 2 2 9 9 5 C on A 2 2 9.0 10 N m /C 1.0 10 C 4.0 10 C 9.0 10 N 2.0 10 m F × × × = = × × The net force on A is ( 29 ( 29 ( 29 5 5 on A B on A C on A ˆ ˆ 9.0 10 N 9.0 10 N 0 N F F F i i = + = × + × = r r r 26.18. Model: Objects A and B are point charges. Visualize: Because there are only two charges A and B, the force on charge A is due to charge B only, and the force on B is due to charge A only. Solve: Coulomb’s law gives the magnitude of the forces between the charge. Thus, F A on B = F B on A = 9.0 × 10 9 N m 2 /C 2 ( 29 20.0 × 10 9 C ( 29 10.0 × 10 9 C ( 29 2.0 × 10 2 m ( 29 2 = 4.5 × 10 3 N Because the charge on object A is positive and on object B is negative, F B on A is upward and F A on B is downward. Thus, r F B on A = + 4.5 × 10 3 ö j N r F A on B =  4.5 × 10 3 ö j N 26.26. Model: A field is the agent that exerts an electric force on a charge. Visualize: Solve: (a) To balance the gravitational force on a proton ( 29 ( 29 net on p p G y F F F Σ = = r r N. This means ( 29 ( 29 ( 29 27 7 on p 19 p 1.67 10 kg 9.8 N/kg 1.02 10 N/C 1.60 10 C G mg F F q E mg E q × = ⇒ = ⇒ = = = × × Because F on p must be upward and the proton charge is positive, the electric field at the location of the proton must also be pointing upward. Thus ( 29 7 1.02 10 N/C, downward . E = × r (b) In the case of the electron, ( 29 ( 29 31 11 19 9.11 10 kg 9.8 N/kg 5.58 10 N/C 1.60 10 C mg E q × = = = × × Because F on e must be upward and the electron has a negative charge, the electric field at the location of the electron must be pointing downward. Thus electron must be pointing downward....
View
Full Document
 Spring '12
 n.a
 Force, Electric charge, Fnet, point charges, Fon

Click to edit the document details