Eli rolled a ball down the cement sidewalk as hard as he could. the ball rolled for less than a minute before it came to a stop. what force acted to slow and finally stop the ball? a. friction, acting in the same direction as the motion of the ball b. the normal force, pushing upward on the ball c. friction, acting in opposition to the motion of the ball d. the normal force, pulling downward on the ball

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

The pressure proportional to the area a- inversely b- directly c- increase d-decrease

Balloon a has charge q, and identical mass balloon b has charge 10q. you hang them from threads near each other. choose all of the statements with which you agree. check all that apply. a. a and b exert the same magnitude forces on each other. b. the force that a exerts on b is 10 times the force that b exerts on a. c. the angle between the thread supporting a and the vertical is < the angle between the thread supporting b and the vertical. d. the force that a exerts on b is 1/10 the force that b exerts on a.