A student determines the focal length of a device ‘x’ by focusing the image of a distant object on a screen placed 20cm from the device on the same side as the object. The device ‘X’ is

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

This is the substance(s) formed in a chemical reaction.

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.