A man pulled a 25.0 kg object 14.0 cm vertically with his teeth. (a) How much work (in J) was done on the object by the man in this lift, assuming the object was lifted at constant velocity? (Include the sign of the value in your answer.)

Name two kinds of practical electric pumps.

Acamcorder has a power rating of 20 watts. if the output voltage from its battery is 9 volts, what current does it use?

The horizontal blue line through the middle of the lens is called the optical axis. as the lamp is moved above or below the axis, keeping the horizontal distance to the center of the lens constant, how does the horizontal distance from the lens to the image change?