Un corp de masă m, așezat pe un plan orizontal fără frecări, este legat de un resort ideal orizontal și, sub acţiunea unei forțe orizontale F, este deplasat la distanţa x, față de poziția de echilibru. Lăsat liber, corpul începe să oscileze armonic. Calculati: a) constanta de elasticitate ka resortului; b) frecvența v a oscilațiilor; c) viteza maximă VM atinsă de corp; d) ecuația de mişcare dacă la momentul inițial corpul este în pozitia de echilibru. Aplicație: m= 250 g; F= 100 N; Xo = 10 mm.

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.