The focal length of the lens of a simple digital camera is 40 mm, and it is originally focused on a person 25 m away. In what direction must the lens be moved to change the focus of the camera to a person 4.0 m away

Alead ball is dropped into a lake from a diving board 5m above the water . it hits the water with a certain velocity and then sink with constant velocity in bottom . it reaches the bottom 5 second after it is dropped if g= 10m/s2 . find depth of the lake and average velocity of the ball ?

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.

An electron is ejected into a horizontal uniform e⃗ field at a parallel horizontal velocity of v0. assume the electron's initial position x0, initial velocity v0, time t, magnitude of electric field e, electron's mass m, and the magnitude of the electron's charge |e|. ignore the force that earth exerts on the electron. assume the e⃗ field is in the same direction as the initial velocity. part a define the equation for the electron's velocity. express your answer in terms of the variables v0, |e|, t, e, and m.