A tennis racket hits a tennis ball. The racket has a mass that is four times greater than the tennis ball. Compared to the force exerted on the ball by the racket, the force exerted on the racket by the ball is A.) four times smaller
B.) the same
C.) 16 times smaller
D.) four times greater

Bone-strengthening physical activity done increases bone-mineral content and bone density in youth.

Copper has free electrons per cubic meter. a 71.0-cm length of 12-gauge copper wire that is 2.05 mm in diameter carries 4.85 a of current. (a) how much time does it take for an electron to travel the length of the wire? (b) repeat part (a) for 6-gauge copper wire (diameter 4.12 mm) of the same length that carries the same current. (c) generally speaking, how does changing the diameter of a wire that carries a given amount of current affect the drift velocity of the electrons in the wire?

Ameter stick is pivoted at the 0.50-m line. a 3.0-kg object is hung from the 0.15-m line. where should a 5.0-kg object be hung to achieve equilibrium (the meter stick oriented horizontal and motionless)?