# 1722 set up like charges repel and unlike charges

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17.22. Set Up: Like charges repel and unlike charges attract. The charges and their forces on are shown in Figure 17.22. Figure 17.22 q 2 q 3 F 1 q 1 F 2 x y 0.300m 0.200m q 3 F 5 k 0 qq r 0 r 2 . 2 y F 5 F 1 1 F 2 5 2.59 3 10 2 6 N F S 2 F S 1 F 2 5 k 0 q 2 q 3 0 r 2 2 5 1 8.99 3 10 9 N # m 2 / C 2 2 1 3.20 3 10 2 9 C 21 5.00 3 10 2 9 C 2 1 0.400 m 2 2 5 8.99 3 10 2 7 N. F 1 5 k 0 q 1 q 3 0 r 1 2 5 1 8.99 3 10 9 N # m 2 / C 2 2 1 1.50 3 10 2 9 C 21 5.00 3 10 2 9 C 2 1 0.200 m 2 2 5 1.69 3 10 2 6 N. x y q 3 F 1 q 1 F 2 0.400m 0.200m q 2 q 3 F 5 k 0 qq r 0 r 2 . 1.73 3 10 2 8 N u 5 32.4°. tan u 5 F y F x 5 9.27 3 10 2 9 N 1.46 3 10 2 8 N 5 0.6349 F 5 " F x 2 1 F y 2 5 1.73 3 10 2 8 N. F y 5 F 1 y 1 F 2 y 5 9.27 3 10 2 9 N. F x 5 F 1 x 1 F 2 x 5 1.46 3 10 2 8 N; F 2 y 5 F 2 sin 65.0° 5 9.27 3 10 2 9 N. F 2 x 5 F 2 cos 65.0° 5 4.32 3 10 2 9 N; F 1 y 5 0. F 1 x 5 1.023 3 10 2 8 N; 17-6 Chapter 17
Solve: The net force has magnitude and is in the direction. 17.23. Set Up: Like charges repel and unlike charges attract. The charges and the forces on the charges and in the dipole are shown in Figure 17.23. Use the coordinates shown. and Figure 17.23 Solve: The net force has magnitude and is in the direction from the to the charge. (b) and each produce clockwise torques and each have a moment arm of 1.50 cm. and each have zero moment arm and produce no torque. The torque is clockwise. Reflect: The x components of the two forces are in opposite directions so they cancel and the net force has no x component. But the torques of and are in the same direction and therefore produce a net torque. F 2 x F 1 x t 5 2 F 1 x 1 0.0150 m 2 5 2 F 1 cos u 1 0.0150 m 2 5 2 1 1.124 3 10 3 N 21 cos 48.6° 21 0.0150 m 2 5 22.3 N # m F 2 y F 1 y F 2 x F 1 x 2 5.00 m C 1 5.00 m C 1.69 3 10 3 N F y 5 F 1 y 1 F 2 y 5 2 2 F 1 sin u 5 2 2 1 1.124 3 10 3 N 2 1 1.50 cm 2.00 cm 2 5 2 1.69 3 10 3 N. F x 5 F 1 x 1 F 2 x 5 0. F 1 5 F 2 5 1 8.99 3 10 9 N # m 2 / C 2 2 1 5.00 3 10 2 6 C 21 10.0 3 10 2 6 C 2 1 0.0200 m 2 2 5 1.124 3 10 3 N. x q 1 q 2 q 3 F 1 F 1 x F 2 x F 2 y F 2 F 1 y y 1.50cm 1.50cm axis 2.00cm u u u 5 48.6°. sin u 5 1.50 cm 2.00 cm q 2 q 1 F 5 k 0 qq r 0 r 2 . 1 x 2.40 3 10 2 7 N F x 5 F 1 x 1 F 2 x 5 1 F 1 2 F 2 5 2.40 3 10 2 7 N. F 2 5 k 0 q 2 q 3 0 r 2 2 5 1 8.99 3 10 9 N # m 2 / C 2 2 1 5.00 3 10 2 9 C 21 0.600 3 10 2 9 C 2 1 0.300 m 2 2 5 2.997 3 10 2 7 N. F 1 5 k 0 q 1 q 3 0 r 1 2 5 1 8.99 3 10 9 N # m 2 / C 2 2 1 4.00 3 10 2 9 C 21 0.600 3 10 2 9 C 2 1 0.200 m 2 2 5 5.394 3 10 2 7 N. Electric Charge and Electric Field 17-7
17.24. Set Up: In the O-H-N combination the is 0.170 nm from the and 0.280 nm from the In the N-H-N combination the is 0.190 nm from the and 0.300 nm from the other Like charges repel and unlike charges attract. The net force is the vector sum of the individual forces. Solve: (a) O-H-N attractive repulsive N-H-N attractive repulsive The total attractive force is and the total repulsive force is The net force is attractive and has magnitude (b) The bonding force of the electron in the hydrogen atom is a factor of 10 larger than the bonding force of the adenine- thymine molecules.