Static (Friction prevents sliding)

In the example below, the action-reaction pair is shown by the arrows (vectors), and the actionreaction described in words. In a through g, draw the other arrow (vector) and state the reaction to the given action. Then make up your own example inh.. Example: ~. ~ .. /'~ - r.h Fist hits wall. Wall hits fist. Bat hits ball. c. _ Athlete pushes bar upward. f. _ Head bumps ball. a. _ Hand touches nose. d. ~_ g. --------- Windshield hits bug. Hand pulls flower. e. h.

Draw arrows to show the chain of at least six parts of action-reaction forces below.

To say the weight of the apple is 1 N is to say that a downward gravitational force of 1 N is exerted on the apple by [Earth] [her hand].

Nellie's hand supports the apple with normal force N, which acts in a direction opposite to W. We can say N [equals W] [has the same magnitude as Wj.

Since the apple is at rest, the net force on the apple is [zero] Lnzero]

Since N is equal and opposite to W, we [can] [cannot] say that Nand W comprise an action-reaction pair. The reason is because action and reaction always [act on the same object] [act on different objects], and here we see Nand W [both acting on the apple] [acting on different objects].

In accord with the rule, "If ACTION is A acting on B, then REACTION is B acting on A," if we say action is Earth pulling down on the apple, then reaction is [the apple pulling up on Earth] [N, Nellie's hand pushing up on the apple].

To repeat for emphasis, we see that Nand Ware equal and opposite to each other [and comprise an action-reaction pair] [but do not comprise an action-reaction pair].

Another pair of forces is N as shown, and the downward force of the apple against .:~ Nellie's hand, not shown. This force pair [is] [isn't] an action-reaction pair.

Suppose Nellie now pushes upward on the apple with a force of 2 N. The apple [is still in equilibrium] [accelerates upward], and compared to W, the magnitude of N is [the same] [twice] [not the same, and not twice].

Once the apple leaves Nellie's hand, N is [zero] [still twice the magnitude of W], and the net force on the apple is [zero] [only W] [still W - N, a negative force]. .

To the right we see the top views of 3 motorboats crossing a river. All have the same speed relative to the water, and all experience the same water flow. Construct resultant vectors showing the speed and direction of the boats. a. Which boat takes the shortest path to the opposite shore? b. Which boat reaches the opposite shore first? c. Which boat provides the fastest ride?

She tosses the ball along the dashed path. The velocity vector, complete with its horizontal and vertical components, is shown at position A. Carefully sketch the appropriate ..... components for positions Band C. a. Since there is no acceleration in the horizontal direction, how does the horizontal component of velocity compare for positions A, B, and C? b. What is the value of the vertical component of velocity at position B? c. How does the vertical component of velocity at position C compare with that of position A?

It is important to distinguish between force and velocity vectors. Force vectors combine with other force vectors, and velocity vectors combine with other velocity vectors. Do velocity vectors combine with force vectors?

All forces on the bowling ball, weight (down) and support of alley (up), are shown by vectors at its center before it strikes the pin a. Draw vectors of all the forces that act on the ball b when it strikes the pin, and c after it strikes

Sliding at constant speed without friction

Decelerating due to friction

Static (Friction prevents sliding)

Rock slides (No friction)

Static

Rock in free fall

Falling at ten~inal velocity