2nd Semester Interim Review

The Law of Universal Gravitation and Coulomb’s Law for electrostatic forces are often compared. Which answer most completely describes the difference/s between the gravitational force and the electrostatic force?

• The gravitational force can only attract but the electrostatic force can attract or repel

• The gravitational force is much weaker than the electrostatic force

• The gravitational force is weaker and can only attract objects but the electrostatic force is strong and can both attract and repel

• The gravitational force occurs throughout the universe but the electrostatic force only occurs on Earth

Tags

NGSS.HS-PS2-4

What is a strength and limitation of this model comparing the Gravitational Force and the Electrostatic Force?

• Strength: The model shows how the direction of the force differs. Weakness: The model does not correctly show how distance impacts Gravitational and Electrostatics forces.

• Strength: The model shows how the direction of the force differs. Weakness: The model does not show that the Electrostatic Force is much stronger than the Gravitational Force

• Strength: The model shows that distance is a factor in both Weakness: The model does not correctly show the direction of the two forces

• Strength: The model shows that distance is a factor in both . Weakness: The model does not correctly show how mass or charge impact the two forces.

This model was presented to aid students in comparing and contrasting the Gravitational and Electrostatic Forces. The teacher told the students that there was missing information. What should the students add to the model and why?

• Add arrows of equal lengths to all models because the forces are equal. All arrows should be pointing toward one another because the strength of these two types of forces is equal and forces are always attracting.

• Add arrows of equal lengths to all models. Arrows for gravitational force should point toward one another. Arrows for electrostatic force should be drawn toward each other for oppositely charged objects and away from each other for like charged objects.

• Add short arrows of equal length to the gravitational force model and long arrows of equal length to the electrostatic model. Arrows for gravitational force should point toward one another. Arrows for electrostatic force should be drawn toward each other for oppositely charged objects and away from each other for like charged objects.

• Increase distance between two objects for the gravitational force model. Shorten the distance between the charged objects because the electrostatic force only works at short distances.

Two charged objects are held 1 meter apart from each other. Then they are moved to 2 meters apart. How is the electrostatic force and gravity force between them affected by this move?

• Both forces will be ¼ as strong after the move.

• Both forces will be ½ as strong after the move.

• Gravity will be ½ as strong and the electrostatic force will be ¼ strong.

• Gravity will be ¼ as strong and the electrostatic force will be ½ as strong.

Tags

NGSS.HS-PS2-4

Electrostatic force F exists between two point charges with a separation distance d. Which model best represents the relationship between force and distance?

• Figure 1 because force and distance have inversely proportional relationship.

• Figure 1 because force and distance are directly proportional relationship.

• Figure 2 because force and distance have an inverse squared relationship.

• Figure 2 because force and distance have an exponential, direct relationship.

An inflated balloon which has been rubbed against a person’s hair is touched to a neutral wall and remains attracted to it. Which picture correctly represents the charge distribution on the balloon and the wall.

• Image A is correct because the top and bottom of the balloon have less charge.

• Image B is correct because the while there are still positive charges in the balloon, they are repelled by the positive charges in the wall

• Image C is correct because there is not enough charge in the balloon to completely repel all of the negative charges on the wall’s surface

• Image D is correct because the negative particles in the wall will be attracted to the positive charges on the other side of the balloon.

Tags

NGSS.HS-PS2-4

A group of students are conducting an investigation about charging through the process of friction. The students rub two neutral materials together, and there is a transfer of electrical charge from one material to the other. What is the net electrical charge of the objects?

• The net electrical charge is positive as electrons are transferred from one material to the other.

• The net electrical charge is positive as protons are transferred from one material to the other.

• The net electrical charge remains neutral as electrons are transferred from one material to the other,

• The net electrical charge remains neutral as protons are transferred from one material to the other.

Tags

NGSS.HS-PS3-5

An uncharged balloon was hanging from the ceiling. A positively charged rod was brought close to, but never touching it, the balloon was attracted to the rod as shown. When the positively charged rod is removed and replaced with a negatively charged rod, what will the balloon do and why?

• The balloon will be attracted to the negatively charged rod because it has the opposite charge of the positively charged rod.

• The balloon will be attracted to the negatively charged rod because the charges will separate on the surface of the balloon.

• The balloon will be repelled by the negatively charged rod because it has the opposite charge of the positively charged rod.

• The balloon will be repelled by the negatively charged rod because the charges will separate on the surface of the balloon.

Tags

NGSS.HS-PS2-4

According to the Law of Conservation of Electric Charge, which scenario could NEVER occur?

• The total charge on an object change

• Net charge has been created or destroyed

• One object has more charge than another

• The total amount of charge on an object increases

What is potential difference?

• the difference in electric potential (Voltage) between the final and the initial location when work is done upon a charge to change its potential energy

• the difference in gravitational pull between the final and initial location when work is done upon a charge to change its potential energy

• the difference in resistance (R) between the final and the initial location when work is done upon a charge to change its potential energy

• the difference in current (I) between the final and the initial location when work is done upon a charge to change its potential energy