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Get the assessment: FA16.2.docx
Get the Practice Problems: Worksheet-ProblemsFromA16.2.docx
The Assessment solved:
1. A uniform electrical field exerts a force of 0.890 N to the left on a -410. µC charge. What is the change in electrical potential if you move 2.60 m to the left? Is it an increase in potential, or a decrease?
(5640 V, increase)
2. If you move a mass vertically from point A to point B in a uniform gravitational field, the potential changes from -12.0 J/kg to +23.0 J/kg in a distance of 17.0 m. What force does the field exert on a 5.20 kg mass, and which point is at a higher elevation, A or B? Does the field point toward A or B?
(10.7 N, B is higher, toward A)
3. What is the electric field 34.5 cm above a -12.0 mC charge?
(9.06x105 N/C down)
(Like Practice 11-20 below)
5. Find the electric field at point p. Draw the electric field vector, and label its magnitude and direction. Charge A is -1.80 µC, B is +2.60 µC, and each grid line is a meter.
(1560 N/C left and up at 66.7o with the x axis)
<--- Ben Nickle's treatise on how to do all of this using matrices!!
More Practice Problems:
Problems from A16.2 Vector Fields: (Assume all these fields are uniform)
1. A gravitational field increases the potential of a mass from 35.0 J/kg at point A to 89.0 J/kg at point B in a vertical distance of 2.50 m. What is the field strength, and what force does it exert on a 23.0 kg mass? Does the field point toward B or A? (21.6 N/kg, 497 N, toward A)
2. An electric field exerts a Southerly force of 1.30 N on a +780. µC charge. What is the change in potential if you displace yourself 5.30 m to the north? (+8830 V)
3. A gravitational field exerts a force of 140. N on a 17.0 kg mass away from point B and toward point A that is vertically displaced from B a distance of 45.0 m. What is the field strength? What is the change in gravitational potential if you go from B to A? (8.24 N/kg, -371 J/kg)
4. An upward electric field has a strength of 23,400 N/C. What is the change in potential if you displace yourself upward 3.40 cm? What force will it exert on an electron? A proton? (-796 J/C or V, 3.75x10-15 N down, 3.75x10-15 N up)
5. If you move 12.0 m West in an electrical field, your electrical potential drops by 340. V. What is this electrical field? What force does this field exert on a charge of -56.0 µC? (28.3 V/m (or N/C) to the West, 1.59x10-3 N East)
6. A gravitational field has a strength of 1.10x10-7 N/kg to the right. If I move a mass 2.30 m to the left, what is the change in gravitational potential? What force does this exert on a 1.00 gram object?
(+2.53x10-7 J/kg, 1.10x10-10 N)
7. An electrical field changes electrical potential from 210. V to 560. V when you move down 4.50 cm. What is the magnitude and direction of the electrical field, and what force does it exert on a +2.40 µC charge? (7780 V/m (or N/C) up, 0.0187 N up)
8. An electrical field exerts a force of 78.0 N to the left on a -12.0 µC charge. What is the magnitude and direction of this electrical field? What is the change in electrical potential if you move 13.0 cm to the left? (6.50x106 N/C right, +8.45x105 V)
9. The leftmost of two vertical parallel plates is held at -12.0 V, and the rightmost is held at +16.0 V. If they are separated by 3.20 cm, what is the electrical field between them? What force would it exert on an electron between the plates? (875 V/m to the left, 1.40x10-16 N to the right)
10. If you move a mass vertically from point A to point B, the potential changes from -45.0 J/kg to -12.0 J/kg in a distance of 3.40 m. What is the gravitational field strength, and which point is at a higher elevation, A or B? Does the field point toward A or B? (g = 9.71 N/kg toward A, B is higher)
11. The electric field is 52.0 N/C downwards 54.0 cm above a charge. What is the charge, and is it positive or negative? (-1.69x10-9 C, negative)
12. What is the electric field 230. m above a +21.0 µC charge? What direction is it? (3.57 N/C up)
13. Near a -18.0 mC charge there is an upward electric field of 450. N/C. How far away is the point where this happens, and where is it, above or below the charge? (19.0 m, below)
14. There is an electric field of 310. N/C upwards 88.0 cm above an unknown charge. What is the charge, and is it positive or negative? (2.67x10-8 C, positive)
15. What is the electric field 2.70 m to the left of a +8.20 mC charge? What direction is it? (1.01x104 N/C, left)
16. At what distance from the center of a 6.90x1024 kg planet is the gravitational field 4.50 N/kg? (1.01x107 m)
17. What is the acceleration of gravity on the surface of a planet with a mass of 6.39x1023 kg and a radius of 3.39x106 m? (Mars) (3.71 N/kg)
18. What is the gravitational field 4.50 m to the right of a 2.80x1012 kg point mass? What direction? (9.22 N/kg left)
19. Near a 3.40x1012 kg point mass there is a field of 5.60 N/kg to the left. What distance are we from the point mass, and where is the mass in relation to us? (6.36 m, the mass is to our left)
20. There is a gravitational field of 14.0 N/kg to the right, 7.20 m from a point mass. What is the mass, and where are we in relation to the mass? (1.09x1013 kg, we are to the left of the mass)
B. Find the gravitational field at p and q: (p: 10.7 N/kg right, q: 28.3 N/kg left)
D. Find the electrical field at p and q: (p: 54.9 N/C right, q: 2.01 N/C right)
22. Each grid line is a meter. Calculate the field at point p.
B. Mass A is 9.40x1012 kg, mass B is 1.80x1012 kg
D. Mass A is 1.40x1012 kg, mass B is 1.20x1012 kg
14.4 N/kg to the right and up at 54.9o with the x axis
E. Charge A is -3.70 µC, B is +5.30 µC
4970 N/C right and up (barely) at 1.26o with the x axis
F. Mass A is 2.90x1012 kg, mass B is 8.70x1012 kg
49.8 N/kg left and down at 62.8o with the x axis
Instruction for this unit:
Basic Fields
5:10Electric Fields around Point Charges 2
Electric Fields around Point Charges Example 1
Electric Fields around Point Charges Example 2
Electric Fields around Point Charges Example 3
Electric Fields around Point Charges Example 4
Fields in Arrays of charge:
Overview and steps, Labeling E-Fields:
3:17Vector Fields with Points(1/4)
Step 1 - Calculating the Magnitudes:
3:12Vector Fields with Points(2/4)
Step 2 - Finding the Trig Angles:
2:25Vector Fields with Points(3/4)
Step 3 - Do Vector Addition:
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