Quick, this is for my lifeskills class

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

Work out sian speed for the first 30 minutes of her journey. give your answer in km/h.

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 ?