CH. 4 -- 4, 10,  14, 22, 28,  32, 38, 44, 46, 54  QUIZ 5
4.

(a) 69.3 N.

(b)34.6 N
10. (a) 90.9 kg (b) 22.0 m
14. (a) .11.0 N  This maximum occurs in the interval t = 0 to t = 2.00 s
(b) The net force is zero when the acceleration is zero. This is between 2.00 s and 6.00 s.|
(c)2.75 N
22.

(a) the earth (gravity)

(b) 4 N; the book

(c) no, these two forces are exerted on the same object

(d) 4 N; the earth; the book; upward

(e) 4 N, the hand; the book; downward

(f) second (The two forces are exerted on the same object and this object has zero acceleration.)

(g) third (The forces are between a pair of objects.)

(h) No. There is a net upward force on the book equal to 1 N.

(i) No. The force exerted on the book by your hand is 5 N, upward. The force exerted on the book by the earth is

4 N, downward.

(j) Yes. These forces form a third-law pair and are equal in magnitude and opposite in direction.

(k) Yes. These forces form a third-law pair and are equal in magnitude and opposite in direction.

(l) One, only the gravity force.

(m) No. There is a net downward force of 5 N exerted on the book.
28.  SEE DISCUSSIONS.

(a) If the table is frictionless there is a net horizontal force on the combined object of the two blocks,

and block B accelerates in the direction of the pull. The friction force that B exerts on A is to the right, to try to

prevent A from slipping relative to B as B accelerates to the right. . f is the friction force that B exerts on A and n is the normal force that B exerts on A.

(b) The pull and the friction force exerted on B by the table cancel and the net force on the system of two blocks is

zero. The blocks move with the same constant speed and B exerts no friction force on A. .
32  (b) 279 N .
38

0.17 m/s,

and the oil should be safe.
44. 

(a) The force the astronaut exerts on the cable and the force that the cable exerts on the astronaut are
an action-reaction pair, so the cable exerts a force of 80.0 N on the astronaut.
(b) The cable is under tension.
(c) 0.762 m /s2. 
(d) There is no net force on the massless cable, so the force that the spacecraft exerts on the cable must be 80.0 N

(this is not an action-reaction pair). Thus, the force that the cable exerts on the spacecraft must be 80.0 N.
(e) 8.84 10-4 m /s2.

46.
(a) The velocity of the spacecraft is downward. When it is slowing down, the acceleration is upward.

When it is speeding up, the acceleration is downward.

(b) In each case the net force is in the direction of the acceleration. Speeding up: w>F and the net force is

downward. Slowing down: w<F and the net force is upward.

(c) 16.0 X 10 3 N.
54. (b) 3.53 m/s2. (c)  120 N (d)  93.3 N