A rod of length L carries a charge Q uniformly distributed along its length.

Find the electrical field at point P on the axis of the rod, a distance a away from the end of the rod.

# AP Physics

# The rod is “flying” above the cable

A conducting rod of length l, mass m, and resistance R is suspended by two vertical conducting wires of lengths d each. The circuit consists of a battery ε, the horizontal fixed wires, two parallel vertical wires , and the conducting rod. All conducting wires have negligible resistance and mass. There is a conducting long cable. The cable is below the rod and at a distance x.

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# The equation of radioactive decay

The half-life of Molybdenum-93 is 4000 years. A sample of Molybdenum-93 has a mass of 10 mg. When will the mass be reduced to 1 mg?

Image Source: Virtual museum of chemical elements.

# A ball is attached to a string and swung so that it travels in a horizontal circle

A ball of mass 0.2 kg is attached to a massless string 1 m long and swung so that it travels in a horizontal circle of radius 0.5 m.

a) Draw a free-body diagram.

b) Find the force of tension in the string as the ball swings in a horizontal circle.

c) Find the period of the ball’s motion.

# To determine the acceleration due to gravity by means of a conical pendulum

A student conducted an experiment to measure the acceleration of gravity. He used a conical pendulum. The conical pendulum is a string with a bob (weight) that revolves around an axis through its point of suspension.

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# A block and a triangular wedge move together

A block of mass m and a triangular wedge of mass M move together without slipping due to a pulling force F. The triangular wedge has a slope α. There is no friction between any pair of surfaces. Derive an equation of pulling force.