A60-kilogram man holding a 20-kilogram box rides on a skateboard at a speed of positive 7 meters per second. he throws the box behind him, giving it a velocity of negative 5 meters per second, with respect to the ground. what is his velocity, in meters per second, after throwing the object?

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=