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1. Find the magnitude and sign of the point charge at the origin

Homework Statement The value of the Electric field at a distance of 82.8 m from a point charge is 75.3 N/C. Its direction is radially in toward the charge. The Coulomb constant is 8.98755 E9. Find the magnitude and sign of the point charge at the origin. Answer in units C. Homework...
2. Magnitude of force. need help solving for x

Homework Statement http://img237.imageshack.us/img237/9041/snapshot20080325182105oh7.th.jpg [Broken] Homework Equations I don't know what to do without having x cancel out. The Attempt at a Solution Homework Statement Homework Equations The Attempt at a Solution
3. Strength of electrostatic force

Homework Statement Three point charges are located at the corner of an equilateral triangle. The Coulomb constant is 8.98755 X 109 N*m2 / C2 What is the strength of the electrostatic force on the top charge? Answer in units of N. Length of each side is .19m Photo...
4. Magnitude of electric force

Homework Statement Four point charges are placed at the four corners of a square. Each side of the square has a length L. Find the magnitude of the electric force on q2 due to all three charges q1 , q2 , q3 and q4. Given L=1 and q= 1.38 μC. Answer in N...
5. Spring constant of molecule

Homework Statement A molecule of DNA lies along a straight line. It is 1.12 μm long. The ends of the molecule become singly ionized; negative on one end, positive on the other. The helical molecule acts as a spring and compresses .4% upon becoming charged. The Coulomb constant is 8.99 X...
6. Doppler effect bat

Homework Statement Assume: Take the speed of sound in air to be 341 m/s. A bat, moving at 6.3 m/s, is chasing a flying insect. The bat emits a 47 kHz chirp and receives back an echo at 47.73kHz. At what speed is the bat gaining on its prey? Answer in units of m/s. Homework Equations...
7. Physics: doppler effect (observer & source in motion)

Homework Statement A train is moving parallel and adjacent to a highway with a constant speed of 25 m/s. A car, at time t0, is 42 m behind the train, traveling in the same direction as the train at 49 m/s, and accelerating at 4 m/s^2. The train's whistle blows at a frequency of 460Hz. The...