How fast is a wave traveling that has a WAVELENGTH of 3 meters and a Frequency of 50 Hz?

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

He viscosities of several liquids are being compared. all the liquids are poured down a slope with equal path lengths. the liquid with the highest viscosity will