Bellringer 2/8

1. Bellringer 2/8 • Two objects are 5.29x10-11 m apart. One object has a mass of 1.67x10-29 kg and the other has a mass fo 9.11x10-31 kg. Calculate the force of gravity between them. Is this force going to affect either object much? • What are the two components needed for a planet to orbit a star? • Besides planets and stars, where else have you seen something like orbits? (think small)

2. Bellringer 2/11 • What is a vector? Give at least two examples of a vector. • Which force has the greatest magnitude in the force diagram below? • What does every number in physics need to be useful? • What does the “nC” represent underneath the charges in the simulation?

3. Bellringer 2/12 • How did the red arrow change as you moved the sensor away from the charge? Closer? • How did the red arrow change as you added more charges? • How were the white arrows further from the charge different from white arrows closer to the charge? How were they the same? • How did the white arrows change as you added more charges on top of each other? • How are the red arrow and the white arrows related?

4. Bellringer 2/13 • Two objects are both positively charged. One has a charge of 7.19 C and the other has a charge of 3.84 C. What is the coulomb force between them if they are 2.61 m apart? • Which of the following charges are positive? • Which charge has the strongest electric field? Which has the weakest?

5. Bellringer 2/15 • A negative charge of -.082 C is placed in a field and experiences a force of 6.1 N. What is the strength of the electric field? • A positively charged object creates an electric field with a magnitude of 4.2 N/C at a distance of 8.32 m. What is the charge on the positive object? • A 6.17 C is placed in a field that is created by a negatively charged object. The positive charge experiences a force of 2.19 N. • Is the positive charge the test or the source? How do you know? • Calculate the strength of the electric field. • The charges are 9.38 m apart. Calculate the charge of the negative object.

6. Bellringer 2/20 • An electric field is pointing straight up. Which direction will the force on a negative charge point? • Which method of charging is modeled in the image to the right? • A positive charge experiences a force to the right. If this force is caused by another positive charge, where must that positive charge be located? • If the first charge is a test charge, which direction will the field it experiences be pointing? • Why do charges in electric fields begin moving?

7. Bellringer 2/21 • What would the electric field lines look like for two negative charges close to each other? • Calculate the field strength 8.91 m away from a -.083 C charge. • A negative object in an electric field experiences a force of 7.12 N to the left. The electric field has a strength of 2.17 N/C. • What is the charge on the negative object? • Which way is the electric field pointing? • What is the value of qtest?

8. Bellringer 2/22 • A negative particle in an electric field experiences a force to the left. Which way is the electric field pointing? • An unknown charged particle placed in an electric field that points straight down. The particle is observed to begin moving straight up. What is the sign of the charge on the particle? • Sketch a diagram of charging by induction.

9. Bellringer – 2/25 (1st and 2nd) • An electric field is pointing directly to the right. Then, two charged particles are placed in the electric field. After being released, one particle begins moving directly to the left and the other begins moving directly to the right. What are the signs of the charges on the particles? • Sketch the electric field lines for two same sign charges, like in the image to the right • Sketch the magnetic field lines for a bar magnet. • What would the field lines look like if we brought the north poles of two magnets close together?

10. Bellringer 2/25 (3rd and 6th) • What will the electric field lines do when there are two source charges close to each other? (hint: what can electric field lines never do?) • Calculate the electrostatic force between two particles that are 4 m apart if one particle has a charge of 4 C and the other is a neutral particle. • What do you know about electromagnets?

11. Bellringer 2/27 • What are the units for electric field? Force? Charge? • Two charged objects have charges of 7.4x10-7 C and 9.52x10-4 C. The electrostatic force between them is measured to be 2.59 N. Calculate the distance between the two charges. • What are two ways to increase the electrostatic force between two charged objects? • The electrostatic force between two objects is measured to be 20N. If the distance between the two objects is doubled, what will be the new electrostatic force?

12. Bellringer – 2/28 • Two charged particles exert a force of 7.83 N on each other. If one particle has a charge of -1.17 C and the charges are 1.2m away from each other, what is the charge of the other particle? • What is the electric field strength 4.85 m away from a -0.051 C charge? • A charged particle is placed in an electric field with a magnitude of 1.04 N/C and experiences a force of 0.84 N. What is the charge on the particle? • A charged particle is placed in an electric field and experiences a force of 2.18 N. The electric field has a strength of 3.8 N/C at a distance of 7.53 m from the source of the field. What is the charge of the particle if it is 7.53 m away from the source?