3. Two small metal spheres are 25.5 cm apart. The spheres have equal amounts of

Question

3.   Two small metal spheres are 25.5 cm apart. The spheres have equal amounts of negative charge and repel each other with a force of 0.034 N. What is the charge on each sphere?

__________C

4. A +2.1-nC point charge is 3.8 cm away from a ?3.3-nC point charge.

(a) What are the magnitude and direction of the electric force acting on the +2.1-nC charge?

__________N

(b) What are the magnitude and direction of the electric force acting on the ?3.3-nC charge?

__________N

__________N

(a) If a pore opens, which way do sodium ions (Na+) flow

Explanation / Answer

3)
force = k * q^2 / r^2
0.034 = 9 * 10^9 * q^2 / 0.255^2

so.. charge = q = 4.9563*10^-7 C

4) a) force on 2.1 nC = 9*10^9 * 10^-18 * 2.1 * 3.3 / 0.038^2 = 4.319252 * 10^-5 N
direction = towards 3.3 nC

b) force = 9*10^9 * 10^-18 * 2.1 * 3.3 / 0.038^2 = 4.319252 * 10^-5 N
direction = towards 2.1 nC

5)
magnitude = 1.5 * 10^6 * 6.3 * 10^-7 = 0.945 N
direction = east

6) as electric foeld is directed into the cell as Na+ has +ve charge .. so it will flow into the cell
a) into the cell
b) magnitude of force = 6 * 10^6 * 1.6 * 10^-19 = 9.6 * 10^-13 N

7)

force on electron = charge * field = 1.6 * 10^-19 * 6800 = 1.088 * 10^-15 N

mass of electron = 9.1 * 10^-31 kg

so acceletiaon = force / mass = 1.088 * 10^-15 / ( 9.1 * 10^-31 ) = 1.1956 * 10^15 m/sec2

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