(Answered) Physics Gizmos Student Exploration: Coulomb Force (Static)

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Student Exploration: Coulomb Force (Static)

Vocabulary: Coulomb’s law, electrostatic force, vector


Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
Have you ever taken clothes out of the dryer and found a sock stuck to your underwear? Static
cling is an example of electrostatic forces, or the forces that exist between charged objects.

1. How do you think the sock and underwear became charged? The sock and the underwear

became charged because they have different charges.


2. Suppose two socks acquire the same charge. Do you think they would stick together? No_

Explain: _Because they would repel each other since they have the same charge.


Gizmo Warm-up
As clothes are tumbled in a dryer, electrons are
rubbed off some items, giving them a positive charge,
and deposited on other items, giving them a negative
charge. These charged items exert electrostatic
forces on one another. You can explore these forces
with the Coulomb Force (Static) Gizmo™.

In its initial settings, the Gizmo shows two objects that each have a charge (q) of 10.0 × 10-4 C
(coulombs). Turn on the Show force vector checkboxes for objects A and B. The arrows
coming from each object are vectors that represent the electrostatic force. The direction and
length of each vector show the direction and magnitude (strength) of each force.

1. Are the vectors for objects A and B pointing together or away from each other? _Away_


2. Are objects A and B attracted together or repelled apart?


3. Compare the lengths of the vectors. What do you notice?

, Get the Gizmo ready:
Activity A:
• Turn on Show grid. Place object A on the x-axis at
The effect of -5 and object B on the x-axis at +5.
charge • Check that Show force vector is turned on for
each object.

Question: How does charge affect the strength of the electrostatic force?

1.
Observe: You can change the charge of each object by entering the desired value in the qA
and qB boxes. Observe the force vectors for each of the situations listed in the table below.
Based on the force vectors, state whether the objects are repelled from one another,
attracted to one another, or if there is no force at all.

qA qB Attraction, repulsion, or no force?
-4 -4
1.0 × 10 C 1.0 × 10 C Repulsion
-1.0 × 10-4 C 1.0 × 10-4 C Attraction
-1.0 × 10-4 C -1.0 × 10-4 C Repulsion
1.0 × 10-4 C 0.0 × 10-4 C No force


2.
Make a rule: Complete the following sentences with the words “attract,” “repel,” or “zero.”

When the charges are the same, the two objects repel one another.

When the charges are opposite, the two objects attract one another.

When one of the objects has no charge, the resulting force is zero.


3.
Predict: How do you think the magnitude of the electrostatic force between two objects will

change if the charge of each object was doubled? The magnitude of the electrostatic

force would be doubled which would make in increase.
4.
Measure: Turn on Show vector notation for both objects. Set the charge of objects A and
B to 1.0 × 10-4 C. The force on object A is now -0.90i + 0j N. That means that the force is
-0.90 N in the x direction and 0 N in the y direction.

A.
What is the magnitude of the force on object A? |FA| = 0.90i

B.
What is the magnitude of the force on object B? |FB| = 0.90i

C.
The force on object A is negative. What does this indicate about the direction of the

force? _It’s going in the opposite direction.