La desviación típica de la altura de los habitantes de un país es de 8 cm. Calcular el tamaño mínimo que ha de tener una muestra de habitantes de dicho país para que el error cometido al estimar la altura media sea inferior a 1 cm con un nivel de confianza del 90%.

An electrical motor raises a 50kg load at a construct velencity .calculate the power of the motor, if it takes 40sec to raise the load through a height of 24m(take g =9.8n/g)

Afluid flows with a velocity field given by v=(x/t)i.. determine the local and convective accelerations when x=3 and t=1.

Consider a large isothermal enclosure that is maintained at a uniform temperature of 2000 k. calculate the emissive power of the radiation that emerges from a small aperture on the enclosure surface. what is the wavelength ? , below which 10% of the emission is concentrated? what is the wavelength ? 2 above which 10% of the emission is concentrated? determine the wavelength at which maximum spectral emissive power occurs. what is the irradiation incident on a small object placed inside the enclosure?