Un muelle se alarga 5 cm, cuando de él se cuelga una masa de 1000 gr. Colocamos después este muelle unido a una masa de 500 g sobre una mesa horizontal sin rozamiento. La masa se separa 3 cm de su posición de equilibrio y se deja vibrar sobre el eje horizontal. Calcular: a) La fase inicial y la amplitud del movimiento.
b) La elongación y la velocidad en el instante t = 0,5 s
c) La velocidad angular
d) El periodo
e) la constante de recuperación del resorte;
f) El valor máximo de la velocidad.
g) la energía potencial en el punto de máxima deformación en horizontal;
h) La energía cinética cuando x = 2 cm;
i) La aceleración de la partícula 0,25 s después de iniciado el movimiento
j) la velocidad cuando el tiempo es de 1 seg

Imagine you work as a consultant, and your daily job involves listening to the constructive criticism of others. as part of your job, you must listen to opposing viewpoints to make important decisions. in this activity, you are a consulting dam engineer. you must make a decision about four different dams; should they be repaired, taken down, or left alone? you will listen to contrasting opinions about what should be done with the dams before you make the final decision. as the consulting dam engineer, what do you decide to do with this dam? explain your reasoning. by making your decision, did you support the opinions of the mayor and/or the dam safety official? why or why not? (site 1)

In a thunderstorm, charge builds up on the water droplets or ice crystals in a cloud. thus, the charge can be considered to be distributed uniformly throughout the cloud. for the purposes of this problem, take the cloud to be a sphere of diameter 1.00 kilometer. the point of this problem is to estimate the maximum amount of charge that this cloud can contain, assuming that the charge builds up until the electric field at the surface of the cloud reaches the value at which the surrounding air breaks down. this breakdown means that the air becomes highly ionized, enabling it to conduct the charge from the cloud to the ground or another nearby cloud. the ionized air will then emit light due to the recombination of the electrons and atoms to form excited molecules that radiate light. in addition, the large current will heat up the air, resulting in its rapid expansion. these two phenomena account for the appearance of lightning and the sound of thunder. take the breakdown electric field of air to be eb=3.00ă—106n/c. part a estimate the total charge q on the cloud when the breakdown of the surrounding air is reached. express your answer numerically, to three significant figures, using ďµ0=8.85ă—10â’12c2/(nâ‹…m2) .

**urgent** roberto plans to use two transformers to reduce a voltage of 120 v to 4 v. he uses a transformer that has 300 coils in the primary winding and 50 coils in the secondary winding. he has four other transformers, as listed in the table. which transformer should roberto use to have an ending voltage of 4 v? a- w b-xc- yd- z