Assuming the acceleration due to gravity is 10 m/s2, how fast will a ball be moving after falling 7.3 seconds?

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?

What is the earliest point in the universe that we can observe? why can’t we see back further than this?

Anybody wanna ? (picture included? )