Tut 2 Coulomb

1. Two objects A and B carry charges of -8nC and 2nC.
They are placed a distance of 0,02m apart.
1.1. Calculate the magnitude of the electrostatic force between them.
1.2. Name the law used to calculate the above force.
1.3. Why do both charges experience the same magnitude of force?
1.4. What would happen to the magnitude of the force if the distance between the charges were increased?
1.5. What is the nature of the force?


1.2. Coulombs Law
1.3. Newton's Third Law
1.4. Force would decrease (inverse proportion)
1.5. attractive (unlike charges attract)

2. The magnitude of the electrostatic force between charges X and Y placed 24mm apart,
is exactly 3 x 10-5N.
The charge on X is 6uC.
2.1. What is meant by 6uC?
2.2. Calculate the magnitude of the charge on Y.
2.1.
6 x 10-6C
2.2.

3. Charge A (+8 x 10-6C) is attached to the ceiling by a thin string.
Charge B (-4uC) is balanced in the air 12mm below charge A.


3.1. Calculate the electrostatic force between objects A and B.
3.2. What is the mass of B?
3.1.




3.2.

4. Calculate how far apart two charges of magnitude 5nC each must be placed, so that the electrostatic force between them becomes 4 x 10-7N?
4.

5. Object A is held by a thin silk thread as shown at an angle of 150. The mass of A is 2g. The distance between A and B is 22cm, and the charge of B is +8uC.



5.1. Draw and label all the forces acting on A.
5.2. Calculate the weight of A.
5.3. Calculate the charge of A.


5.1.

Fe = electrostatic force
T = tension
w = weight

5.2.


5.3.


6. The force between charges Q1 and Q2 is F. If the distance between the charges is doubled, what would be the new magnitude of the force?
6. F/4

7. The charge of A is Q and that of B is 3Q. The interacting force has a magnitude of F. If the charge of A is doubled, and that of B is halved, what would be the new force if the distance between them is halved?
7.
4F

8. The force between two charges X and Y of magnitude 3Q and 5Q respectively a distance of r apart, is F. How far apart must the charges be placed, so that that the force becomes 2F if the charge of X is doubled?
8. still r
no change to distance

9. Three charges are arranged in a straight line as shown.



Calculate the resultant force on Y.
9.



10. A 10g pith ball A, carrying a charge of +200nC is placed at the bottom of a tall, narrow glass tube which is on an insulated stand. A second pith ball B of the same mass and carrying the same charge as A is introduced at the top of the cylinder.



If no charge is lost to the surroundings, calculate the height h at which B will be suspended above A.
10.

11. Three charges are arranges in a right angle pattern as shown.


Calculate the resultant force on B.
10.



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