A C-130 Hercules is traveling toward a cliff

Mission highlight

A C-130 Hercules is traveling toward a cliff at the speed of 150 m/s. Its engines emit a tone at frequency f0. We consider that the speed of sound is 340 m/s. What frequency is received by a pilot after reflection from the cliff?

Image Source: U.S. Air Force
Continue reading


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

ExpConPenA 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.
Continue reading

A string around the Earth’s equator


Place a string around the Earth’s equator and pull it snug. Add a length of one meter to the string and push it away from the equator an equidistant amount. What is the largest animal, from the list below, that would now be able to walk under the string?

Flea Mouse Dachshund Calf Horse Elephant
Continue reading

When the fuse blows

FUSEA fuse is a device to avoid the flow of a large current in a circuit. The potential difference across the fuse is negligible. In our circuit, the maximum current allowed through the fuse is 10 A. The light bulbs marked 40 Watt, 110 V. The bulbs connected to a voltage source of 110 V. What is the maximum number of bulbs that can be placed in parallel before the fuse blows?

Continue reading

A block and a triangular wedge move together

Problem20_2A 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.

Continue reading

A charged solid spherical conductor with a charged solid spherical shell

SphericalConductorsA solid spherical conductor has charge + Q and radius R. It is surrounded by a solid spherical shell with charge − Q, inner radius 2R, and outer radius 3R. The objects are isolated in space and the electric potential is zero as the distance from the spheres approaches infinity. Point A is at the center of the inner sphere, Point B is located at R, Point C is located at 2R and point D is located at 3R. All distances are from the center of the inner sphere.
Where is the electric potential maximum?
Where is the electric field maximum?

Continue reading

A system of three objects

3objectsNewton2LawA system is composed of three objects with masses m, 5m and 6m. The coefficient of kinetic friction between the objects m, 5m and the surface is 0.5. Find the acceleration of the objects.
Continue reading