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Ch 22: Electric Charges and Forces
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 22, Problem 20

What is the force F on the 1.0 nC charge in FIGURE EX22.20? Give your answer as a magnitude and a direction.

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Identify the charges and their positions in FIGURE EX22.20. Note the charge values, their distances, and the configuration of the system. The 1.0 nC charge is the one experiencing the net force due to the other charges.
Use Coulomb's Law to calculate the force between the 1.0 nC charge and each of the other charges. Coulomb's Law is given by: F=kq1q2r2, where k is the Coulomb constant, q1 and q2 are the charges, and r is the distance between them.
Determine the direction of each force vector. Remember that like charges repel and opposite charges attract. Use the geometry of the system to resolve the forces into their components along the x-axis and y-axis, if necessary.
Add the force vectors to find the net force on the 1.0 nC charge. Use vector addition: F=Fx+Fy. Combine the x and y components using the Pythagorean theorem to find the magnitude of the net force: F=Fx2+Fy2.
Determine the direction of the net force using trigonometry. The angle θ can be found using θ=tan1FyFx. Express the final answer as a magnitude and direction.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Coulomb's Law

Coulomb's Law describes the electrostatic force between two charged objects. It states that the force (F) is directly proportional to the product of the magnitudes of the charges (q1 and q2) and inversely proportional to the square of the distance (r) between them. The formula is F = k * (|q1 * q2|) / r², where k is Coulomb's constant. This law is fundamental for calculating the force on a charge due to other charges.
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Electric Field

An electric field (E) is a region around a charged object where other charges experience a force. It is defined as the force per unit charge experienced by a positive test charge placed in the field, given by E = F/q. The direction of the electric field is away from positive charges and towards negative charges. Understanding electric fields is crucial for determining the force on a charge in a given configuration.
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Vector Addition

Vector addition is the process of combining two or more vectors to determine a resultant vector. In physics, forces are vectors that have both magnitude and direction. When multiple forces act on a charge, the net force is found by adding the individual force vectors, taking into account their directions. This concept is essential for accurately determining the total force acting on the charge in the problem.
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