Page 282: Questions # 1 to 8 inclusive [answers in bold print]

1.    What factor distinguishes a body's velocity from it speed?

An expression of velocity specifies the direction a body is moving in addition to how fast; speed is merely how fast a body is moving with no reference to direction.

2.    Clarify the definition of linear acceleration of a body or object by giving examples in human movement situations.

Linear acceleration is often confused with velocity; it is the change in velocity during a specified time.  Qualitatively, acceleration is speeding up or changing direction; decelerations is slowing down.  Quantitatively acceleration is the change in velocity divided by the time during which that changed occurred.  Examples in human movment: starting and stoping in any activity, pushing off and landing from a jump, an arrow accelerating during bow recoil and decelerating as it enters a target.

3.    If a body is moving with a constant velocity, what is its acceleration?

Constant velocity means that there is no change in either speed or direction; therefore, the acceleration is equal.

4.    Which runner has the greater acceleration, the one who gains a velocity of 5m/sec in 4 sec or the one who gains a velocity of 4 m/sec in 3 sec?

5/4 = 1.25m/sec/sec and is less than 4/3 - 1.33m/sec/sec

5.    What is the direction of the instananteous velocy of release of a bowling ball if the straight arm is vertical when the fingers releast the ball?  What is the release direction when the arm is 45 degrees beyond the vertical when the ball is released?

The direction of release is tangent to the path of the ball at that instant.  Therefore, at the bottom of the hand's arc, the ball is released horizontally.  If the arm travels another 45 degrees before ball release, the ball's direciton is 45 degrees above the horizontal.

6.    What does the symbol g represent?

The symbol g stands for the acceleration of a body caused by the force of gravity.

7.    What is the vertical velocity component at release of a horizontally projected ball?

An object projected horizontally has zero vertical velocity at the instant of release.  The object will immediately be accelerated downward by gravity after it is released.

8.    State Newton's first law, the law of inertia?

A body at rest will stay at rest, and a body in motion will stay in motion, moving in a constant direction with a constant velocity unless an external force acts on it to change its state of motion.

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Page 288: Questions # 1 to 5 inclusive [answers in bold print]

1.    If your hand applies a force of 45 N (10lb) on a cart, how much force is the cart applying on yoru hand?  According to Newton's third law of action-reaction, if youa re receiving that force from the cart, why are you not forced to move backward?

The equal and opposite reaction force applied by the cart on your hand is 45 N (10lb).  You are not forced to move backward by that 45 N of reaction force on you because the forward friction force of the floor on your feet matches that 45 N. and there is no net external force to move you.

2.    Under the same circumstances given in question 1, how would your motion response differ if youwere on wheels and the cart was not?  What would be the motion response of your body and the cart if you both were on wheels?

If you were on roller skates, that 45N of reaction force would, indeed, cause you to accelerate backward.  Depending on how much friction existed between the cart bottom and the floor, it may or may not move forward.

3.    How is a system's acceleration related to the net force applied to it to the amount of mass that the system has?

The motion response (acceleration) of you and of the cart would depend on your relative masses; the larger the mass, the smaller the acceleration, assuming the same magnitude of net force acted on you and the cart (recall: a=F/m)

4.    If you were to collide with another person who weighted twice as much as you, what would be the rlative magnitude of acceleration of the two bodies?

You would decelerate twice as much as the heavier one you collided with, since each of you received the same force (but in opposite directions) and your mass was half as much as the opponent's mass.

5.    If the force of a tennis racket causes the ball to accelerate forward, what effect does the ball's reaction force have on the reacket?  Which object's motion is more easily changed?  Why?

The equal and opposite reaction force of the ball on the racket would act to decelerate the swinging racket, or, if the player were still applying an accelerating force on the racket, the force of the ball on the racket would permit less racket acceleration than if no force acted to resist that acceleration.

The ball's motion is more easily changed by the impact force it has less mass than the racket held by the player.