A student has an object with a charge of -3 Coulombs. Which of the following objects would have the strongest attraction to object A?(1 point)

Responses

An object with a -3 charge at a distance of 5 cm
An object with a -3 charge at a distance of 5 cm

An object with a +3 charge at a distance of 5 cm
An object with a +3 charge at a distance of 5 cm

An object with a -4 charge at a distance of 2 cm
An object with a -4 charge at a distance of 2 cm

An object with a +3 charge at a distance of 2 cm

1 answer

To determine which object has the strongest attraction to the object with a charge of -3 Coulombs, we can use Coulomb's Law, which states that the force \( F \) between two point charges is proportional to the product of their magnitudes and inversely proportional to the square of the distance between them. The formula is:

\[ F = k \cdot \frac{|q_1 \cdot q_2|}{r^2} \]

where

  • \( F \) is the force,
  • \( k \) is Coulomb's constant,
  • \( q_1 \) and \( q_2 \) are the magnitudes of the charges, and
  • \( r \) is the distance between the charges.

We are interested in attraction, which occurs when one charge is positive and the other is negative.

Let's analyze each option:

  1. An object with a -3 charge at a distance of 5 cm

    • \( |q_1| = 3 \) C, \( |q_2| = 3 \) C, \( r = 0.05 \) m
    • \( F = k \cdot \frac{3 \cdot 3}{(0.05)^2} \)
  2. An object with a +3 charge at a distance of 5 cm

    • \( |q_1| = 3 \) C, \( |q_2| = 3 \) C, \( r = 0.05 \) m
    • \( F = k \cdot \frac{3 \cdot 3}{(0.05)^2} \)
    • This is attractive.
  3. An object with a -4 charge at a distance of 2 cm

    • \( |q_1| = 3 \) C, \( |q_2| = 4 \) C, \( r = 0.02 \) m
    • \( F = k \cdot \frac{3 \cdot 4}{(0.02)^2} \)
  4. An object with a +3 charge at a distance of 2 cm

    • \( |q_1| = 3 \) C, \( |q_2| = 3 \) C, \( r = 0.02 \) m
    • \( F = k \cdot \frac{3 \cdot 3}{(0.02)^2} \)
    • This is also attractive.

Now we will compare the magnitudes of the forces calculated for the attractive cases:

  • For the positive 3 charge at 2 cm: \[ F = k \cdot \frac{3 \cdot 3}{(0.02)^2} = k \cdot \frac{9}{0.0004} = k \cdot 22500 \]

  • For the positive 3 charge at 5 cm: \[ F = k \cdot \frac{3 \cdot 3}{(0.05)^2} = k \cdot \frac{9}{0.0025} = k \cdot 3600 \]

  • For the negative 4 charge at 2 cm: \[ F = k \cdot \frac{3 \cdot 4}{(0.02)^2} = k \cdot \frac{12}{0.0004} = k \cdot 30000 \]

Thus, the strongest attraction comes from:

  • An object with a -4 charge at a distance of 2 cm, yielding the highest force from our calculations.

Final Answer: An object with a -4 charge at a distance of 2 cm.