Section 3 problems 12 - 21

12. (a) and (b)



(c) 5 m / s ^ 2 = a x


13.
(a)


(b) 4.0 N

(c) 11/3 m/s ^2 = a x

14.




(a) 2.0 m / s ^ 2

(b) T = 16 N

15.
(a) 16 N
(b) no acceleration in z-direction
F net external = 20 N

16.(a) 20 N
(b) 20 N
(c) 140 N

17.



(a) 18 m / s ^ 2
(b) to the right
(c) to the left
(d) down
(e) into the center of the circle or up
(f) into the circle or down
(g) acceleration is to the right and the X-axis is to the right.
for all cases F net = 36 N

(h) 56 N
(i) F or at T = + 16 N or it is down
(j) theta = 29 degrees

18. (a) 100 N
(b) 150 N

19.
the elevator accelerates upward, then moves at a constant velocity and finally decelerates and comes to a stop

20. the sphere of the larger mas has the greater acceleration

21. Take the X-axis in the direction of the acceleration or up the plane and the Y-axis perpendicular to it.