Projectile Motion Review
1. An object is undergoing free fall motion. As it falls, the object's ____.
a. speed increases
b. acceleration increases
c. both of these
d. none of these
KEY
2. A football is kicked into the air at an angle of 45 degrees with the horizontal. At the very top of the
ball's path, its velocity is _______.
a. entirely vertical
b. entirely horizontal
c. both vertical and horizontal
d. not enough information given to know.
3. A football is kicked into the air at an angle of 45 degrees with the horizontal. At the very top of the
ball's path, its acceleration is _______. (Neglect the effects of air resistance.)
a. entirely vertical
b. entirely horizontal
c. both vertical and horizontal
d. not enough information given to know.
4. At what point in its path is the horizontal component of the velocity (vx) of a projectile the
smallest?
a. The instant it is thrown.
b. Halfway to the top.
c. At the top.
d. As it nears the top.
e. It is the same throughout the path.
5. At what point in its path is the vertical component of the velocity (vy) of a projectile the smallest?
a. The instant it is thrown.
b. Halfway to the top.
c. At the top.
d. As it nears the top.
e. It is the same throughout the path.
6. Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity ___.
a. decreases
b. remains constant
c. increases
7. A bullet is fired horizontally and hits the ground in 0.5 seconds. If it had been fired with twice the
speed in the same direction, it would have hit the ground in ____. (Assume no air resistance.)
a. less than 0.5 s.
b. more than 0.5 s.
c. 0.5 s.
8. A projectile is launched at an angle of 15 degrees above the horizontal and lands down range. For
the same speed, what other projection angle would produce the same downrange distance?
a. 30 degrees.
b. 45 degrees.
c. 50 degrees.
d. 75 degrees
e. 90 degrees.
9. Two projectiles are fired at equal speeds but different angles. One is fired at angle of 30 degrees
and the other at 60 degrees. The projectile to hit the ground first will be the one fired at (neglect
air resistance) ____.
a. 30 degrees
b. 60 degrees
c. both hit at the same time
10. A projectile is fired horizontally. If the speed is lower, what happens to the time it takes to hit the
ground?
a. increase
b. decrease
c. stay the same
11. Refer to the points on the diagram to explain what is happening to the
vertical velocity of the projectile. (For example you might say it starts at 0
at point A then increases to its maximum at point B and then decreases to
point C)
Highest speed at A  decreases to 0 at point C  increases in the negative
direction until it reaches the same speed it had at A
12. Refer to the points on the diagram to explain what is happening to the
horizontal velocity of the projectile. (For example you might say it starts at
0 at point A then increases to its maximum at point B and then decreases to
point C)
Stays the same throughout the motion
13. Supposing a snowmobile is equipped with a flare launcher that is capable of launching a sphere
vertically (relative to the snowmobile). If the snowmobile is in motion and launches the flare and
maintains a constant horizontal velocity after the launch, then where will the flare land (neglect air
resistance)?
a. In front of the snowmobile
b. behind the snowmobile c. in the snowmobile
14. A zookeeper must shoot a banana from a banana cannon to a monkey who hangs from the limb of a
tree. This particular monkey has a habit of dropping from the tree the moment that the banana
leaves the muzzle of the cannon. If the monkey lets go of the tree the moment that the banana is
fired, then where should she aim the banana cannon? At the monkey
15. Aaron Agin is resolving velocity vectors into horizontal and vertical components. For each case,
evaluate whether Aaron's diagrams are correct or incorrect. If incorrect, explain the problem or
make the correction.
All are incorrect. Vectors MUST
be added tip to tail.
16. How many dimensions does a projectile move in?
a) One
b) Two
c) Three
d) Four
17. True/ False: Projectiles are objects being acted upon by gravity alone. As such, there is a vertical
acceleration but no horizontal acceleration. The horizontal velocity of a projectile is either zero or
a constant nonzero value.
18. True/ False: For any two dimensional motion (whether projectile motion or riverboat problems or
...), perpendicular components of the motion are independent of each other. Any alteration in a
vertical component will not affect the horizontal components of motion.
19. True/ False: The motion along a parabola is not symmetrical.
20. True/ False: Time is different on the x- and y- axis.
21. True/ False: For horizontally launched projectiles, the initial velocity on the y axis will be equal to
the final velocity.
22. Trajectories travel with a parabolic motion due to the influence of gravity.
23. The equation d= v1t + ½ at2 uses the information on which axis?
Y-axis
.
24. What is the equation used to determine range of a projectile? Why is this equation used?
25. A pool ball leaves a 0.60-meter high table with an initial horizontal velocity of 2.4 m/s.
a. Determine the time of flight,
y = viy•t +0.5•ay•t2
-0.60 m = (0 m/s)•t + 0.5•(-9.8 m/s/s)•t2
-0.60 m = (-4.9 m/s/s)•t2
0.122 s2 = t2
t = 0.350 s (rounded from 0.3499 s)
b. Determine the range (ie the horizontal displacement)
d = vt
= (2.4 m/s)(0.3499s)
= 0.84 m
c. Determine the velocity just before it strikes the ground
vertical velocity
horizontal velocity
v2 = v1 + at
v = 2.4 m/s
OR
v22 = v12 + 2ad
v22 = 02 + 2(-9.8)(-0.60)
v22 = 11.76
v2 = ±3.42 m/s
v2 = -3.42 m/s = 3.42 m/s [down]
Therefore the velocity on impact is
c2 = a2 + b2
tan Θ = opp/adj
2
2
= (3.42) + (2.4)
= 3.42/2.4
= 17.46
= 1.425
Θ = 54.9°
v = 4.2 m/s [55°below the horizontal]
d. What variables could be changed so that the pool ball lands further away from the table?
The initial horizontal velocity.
26. A long jumper leaves the ground with an initial velocity of 12 m/s at an angle of 28-degrees above
the horizontal.
a. Determine the horizontal and vertical components of the velocity,
Horiz: vix =(12 m/s) • cos (28 deg) =10.6 m/s
Vert: viy =(12 m/s) • sin (28 deg) = 5.6 m/s
b. Determine the time of flight,
Use vfy = viy + ay • ttotal
0 = 5.6 + (-9.8)(t)
t = 0.571 x 2
t = 1.1 s
OR
vfy = viy + ay • ttotal
-5.6 = 5.6 + (-9.8)(t)
t = 1.1 s
c. Determine the range (ie the horizontal displacement)
v = dt
d = v/t = 10.6/1.14 = 12.2 m
d. Determine the peak height of the football.
ypeak = viy • tup + 0.5 • ay • tup2
= (5.6 m/s)(0.571) + 0.5(-9.8)(0.571)2
= 1.59 m
d = 1.6 m
e. Determine the velocity as it strikes the ground
v = 12 m/s [28°]
f. What variables could be changed so that the long jumper lands further away from the table?
They could jump with a different angle. 45° produces the maximum range.