Honors Physics
Acceleration Due to Gravity
Free Fall
Neglect air resistance in the following Exercises.
1. MC An object is thrown vertically upward. Which of the following statements is true: (a) Its velocity
changes non-uniformly; (b) its maximum height is independent of the initial velocity; (c) its travel time
upward is slightly greater than its travel time downward; (d) the speed on returning to its starting point is the
same as its initial speed? (d)
2.
MC The free-fall motion described in this section applies to (a) an object dropped from rest, (b) an object
thrown vertically downward, (c) an object thrown vertically upward, (d) all of the preceding. (d)
3.
MC A dropped object in free fall (a) falls 9.8 m each second, (b) falls 9.8 m during the first second, (c) has
an increase in speed of 9.8 m s each second, (d) has an increase in acceleration of 9.8 m s2 each second. (c)
4.
MC An object is thrown straight upward. At its maximum height, (a) its velocity is zero, (b) its
acceleration is zero, (c) both a and b. (a)
5.
MC When an object is thrown vertically upward, it is accelerating on (a) the way up, (b) on the way down,
(c) both a and b. (c)
6.
CQ When a ball is thrown upward, what are its velocity and acceleration at its highest point? zero and
2
9.8 m s downward
7.
CQ Imagine you are in space far away from any planet, and you throw a ball as you would on the Earth.
Describe the ball’s motion. The ball moves with a constant velocity
8.
CQ A person drops a stone from the window of a building. One second later, she drops another stone. How
does the distance between the stones vary with time? Increases
9.
 A student drops a ball from the top of a tall building; the ball takes 2.8 s to reach the ground. (a) What
was the ball’s speed just before hitting the ground? (b) What is the height of the building? (a) 27 m s (b)
38 m
10. IE  The time it takes for an object dropped from the top of cliff A to hit the water in the lake below is
twice the time it takes for another object dropped from the top of cliff B to reach the lake. (a) The height of
cliff A is (1) one half, (2) two, (3) four times that of cliff B. (b) If it takes 1.80 s for the object to fall from
cliff A to the water, what are the heights of cliffs A and B? (a) (3) four times (b) 15.9 m and 3.97 m
11.  For the motion of a dropped object in free fall, sketch the general forms of the graphs of (a) v versus t
and (b) y versus t. (a) linear, slope  g (b) parabola
12.  You can perform a popular trick by dropping a dollar bill (lengthwise) through the thumb and forefinger
of a fellow student. Tell your fellow student to grab the dollar bill as fast as possible, and he or she can
have the dollar if able to catch it. (The length of a dollar is 15.7 cm, and the average human reaction time is
about 0.2 s. See Fig. 2.15.) Is this proposal a good deal? Justify your answer. no, not a good deal
13.  A boy throws a stone straight upward with an initial speed of 15 m s. What maximum height will the
stone reach before falling back down? 11 m
14.  In Exercise 96, what would be the maximum height of the stone if the boy and the stone were on the
surface of the Moon, where the acceleration due to gravity is only 1.67 m s2 ? 67 m
15.  The ceiling of a classroom is 3.75 m above the floor. A student tosses an apple vertically upward,
releasing it 0.50 m above the floor. What is the maximum initial speed that can be given to the apple if it is
not to touch the ceiling? slightly less than 8.0 m s
16.  The Petronas Twin Towers in Malaysia and the Chicago Sears Tower have heights of about 452 m and
443 m, respectively. If objects were dropped from the top of each, what would be the difference in the time
it takes the objects to reach the ground? t  0.096 s
17.  You throw a stone vertically upward with an initial speed of 6.0 m s from a third-story office window.
If the window is 12 m above the ground, find (a) the time the stone is in flight and (b) the speed of the
stone just before it hits the ground. (a) 2.3 s (b) 16 m s
Wilson P 62 # 82-100