PHYSICS 114 FINAL (PROJECTILE MOTION UPDATED
ACTUAL QUESTIONS AND CORRECT ANSWERS
Question:
1. A plane is flying at constant speed while the flyer prepares to drop a bomb on the ground. Since there is
no air resistance in the Cartoon World, when he drops the bomb out of the plane which statement best
describes the motion of the bomb relative to the plane?
(a.) The bomb will quickly lag behind the plane. (b.) The bomb will remain under the plane as it falls to the
ground. (c.) The bomb will move ahead of the plane. (d.) The bomb will remain under the plane briefly
before lagging behind.
Answer:
(b.) The bomb will remain under the plane as it falls to the ground. (The speed of the plane and the bomb
are the same in the x-direction).
Question:
2. A cruiser ship simultaneously fires two shots at different targets. Based off of the trajectories shown,
which target will be destroyed first? Ignore air resistance.
(a.) A (higher theta) (b.) B (lower theta) (c.) A and B will be destroyed at the same time. (d.) You need to
know more information, like the speed at which the shots are fired and at what angle then guns are pointed.
Answer:
B. (shorter trajectory/i.e., lower theta)
Question:
3. Which sentence(s) are possibly correct? (a.) Projectiles always accelerate in the horizontal (x) and
vertical (y) directions. (b.) Projectiles always accelerate in the horizontal (x) direction and with a constant
speed in the vertical(y) direction. (c.) Projectiles always move with a constant speed in both the horizontal
(x) and vertical (y) directions. (d.) Projectiles always move with a constant speed in the horizontal (x)
direction and accelerate in the vertical (y) direction.
Answer:
(d.) Projectiles always move with a constant speed in the horizontal (x) direction and accelerate in the
vertical (y) direction.
Question:
4. A poodle and a Dalmatian are playing with a toy near the water. Their owner picks up the toy and tosses
it over the dock and into the water below. The dogs each race after the toy. Both dogs reach the end of the
dock at the same time and jump off towards the toy. The Dalmatian leaps off into the water,but the poodle
got scared at the last second and just dropped straight down. Which statement is true about each dog's
motion?
Answer:
(c.) The poodle and Dalmatian hit the water at the same time, but the Dalmation has the larger speed.
Question:
5. Three projectiles (A, B, and C) are launched with the same initial speed, but at different angles. (a.)
Rank the trajectories in order of increasing horizontal component of velocity. Indicate ties if necessary. (b.)
Rank the trajectories in order of increasing time of flight. Indicate ties if necessary.
, Answer:
(a).the horizontal component of a projectile's velocity is vx=vcosθ. The lower the angle, the greater value
cosθ is.(b). The higher the theta, the more time in the air.
Question:
6. Three projectiles (A, B, and C) are launched with different initial speeds and angles. However, each
projectile reaches the same maximum height. (a.) Rank the trajectories in order of increasing initial
velocity. Indicate ties if necessary. (b.) Rank the trajectories in order of increasing time of flight. Indicate
ties if necessary.
Answer:
A. Each projectile must have the same initial velocity in the y-direction since each one reaches the same
height. But the farther away (horizonally) each projectile lands indicates the strength of its velocity in the
x-direction. Therefore objects that land farther away have greater overall velocities.
B. the total time of flight for each pro-jectile is equal to twice the time needed to fall from its maximum
height. Since all the projectiles reach the same height they all land at the same time.
Question:
7. You are driving a tank around at a constant speed when you spot an enemy tank far off in the
distance.Unfortunately, the soldier controlling your tank's artillery never took physics and accidently fires
a projectile directly upwards (θ= 90 æ ). Using your expert knowledge of projectile motion, determine
which course of action should be taken.
Answer:
Stop the tank immediately. If you stop the tank right away the projectile will continue moving off ahead of
you at the same speed your tank was initially moving at and so will land way ahead of you.
Question:
8. Explain using words only why a projectile fired atθ= 30 æ and a projectile fired with the same speed
atθ= 60 æ both land at the same point.
Answer:
Objects projected atθ= 30 æ have a greater velocity in the x-direction than those fired atθ= 60 æ . The
opposite is true for the velocity in the y-direction (θ= 60 æ is greater thanθ= 30 æ ). And herein lies the
balance:projectiles launched atθ= 30 æ are not in the air longer, but they cover a lot of ground in the
x-direction within that shorter time because their velocity in that direction is greater. On the other hand,
projectiles launched atθ= 60 ædo not cover ground as quickly in the x-direction, but since they are in the
air a much longer time they eventually make it to the same distance away.
Question:
9. What is projectile motion?
Answer:
A projectile motion involves two components of motion -- vertical and horizontal. Characteristically,
motion in one direction is independent of motion in another direction.
Question:
10. A projectile is
Answer:
an object that moves in two dimensions under the influence of gravity and nothing else.
ACTUAL QUESTIONS AND CORRECT ANSWERS
Question:
1. A plane is flying at constant speed while the flyer prepares to drop a bomb on the ground. Since there is
no air resistance in the Cartoon World, when he drops the bomb out of the plane which statement best
describes the motion of the bomb relative to the plane?
(a.) The bomb will quickly lag behind the plane. (b.) The bomb will remain under the plane as it falls to the
ground. (c.) The bomb will move ahead of the plane. (d.) The bomb will remain under the plane briefly
before lagging behind.
Answer:
(b.) The bomb will remain under the plane as it falls to the ground. (The speed of the plane and the bomb
are the same in the x-direction).
Question:
2. A cruiser ship simultaneously fires two shots at different targets. Based off of the trajectories shown,
which target will be destroyed first? Ignore air resistance.
(a.) A (higher theta) (b.) B (lower theta) (c.) A and B will be destroyed at the same time. (d.) You need to
know more information, like the speed at which the shots are fired and at what angle then guns are pointed.
Answer:
B. (shorter trajectory/i.e., lower theta)
Question:
3. Which sentence(s) are possibly correct? (a.) Projectiles always accelerate in the horizontal (x) and
vertical (y) directions. (b.) Projectiles always accelerate in the horizontal (x) direction and with a constant
speed in the vertical(y) direction. (c.) Projectiles always move with a constant speed in both the horizontal
(x) and vertical (y) directions. (d.) Projectiles always move with a constant speed in the horizontal (x)
direction and accelerate in the vertical (y) direction.
Answer:
(d.) Projectiles always move with a constant speed in the horizontal (x) direction and accelerate in the
vertical (y) direction.
Question:
4. A poodle and a Dalmatian are playing with a toy near the water. Their owner picks up the toy and tosses
it over the dock and into the water below. The dogs each race after the toy. Both dogs reach the end of the
dock at the same time and jump off towards the toy. The Dalmatian leaps off into the water,but the poodle
got scared at the last second and just dropped straight down. Which statement is true about each dog's
motion?
Answer:
(c.) The poodle and Dalmatian hit the water at the same time, but the Dalmation has the larger speed.
Question:
5. Three projectiles (A, B, and C) are launched with the same initial speed, but at different angles. (a.)
Rank the trajectories in order of increasing horizontal component of velocity. Indicate ties if necessary. (b.)
Rank the trajectories in order of increasing time of flight. Indicate ties if necessary.
, Answer:
(a).the horizontal component of a projectile's velocity is vx=vcosθ. The lower the angle, the greater value
cosθ is.(b). The higher the theta, the more time in the air.
Question:
6. Three projectiles (A, B, and C) are launched with different initial speeds and angles. However, each
projectile reaches the same maximum height. (a.) Rank the trajectories in order of increasing initial
velocity. Indicate ties if necessary. (b.) Rank the trajectories in order of increasing time of flight. Indicate
ties if necessary.
Answer:
A. Each projectile must have the same initial velocity in the y-direction since each one reaches the same
height. But the farther away (horizonally) each projectile lands indicates the strength of its velocity in the
x-direction. Therefore objects that land farther away have greater overall velocities.
B. the total time of flight for each pro-jectile is equal to twice the time needed to fall from its maximum
height. Since all the projectiles reach the same height they all land at the same time.
Question:
7. You are driving a tank around at a constant speed when you spot an enemy tank far off in the
distance.Unfortunately, the soldier controlling your tank's artillery never took physics and accidently fires
a projectile directly upwards (θ= 90 æ ). Using your expert knowledge of projectile motion, determine
which course of action should be taken.
Answer:
Stop the tank immediately. If you stop the tank right away the projectile will continue moving off ahead of
you at the same speed your tank was initially moving at and so will land way ahead of you.
Question:
8. Explain using words only why a projectile fired atθ= 30 æ and a projectile fired with the same speed
atθ= 60 æ both land at the same point.
Answer:
Objects projected atθ= 30 æ have a greater velocity in the x-direction than those fired atθ= 60 æ . The
opposite is true for the velocity in the y-direction (θ= 60 æ is greater thanθ= 30 æ ). And herein lies the
balance:projectiles launched atθ= 30 æ are not in the air longer, but they cover a lot of ground in the
x-direction within that shorter time because their velocity in that direction is greater. On the other hand,
projectiles launched atθ= 60 ædo not cover ground as quickly in the x-direction, but since they are in the
air a much longer time they eventually make it to the same distance away.
Question:
9. What is projectile motion?
Answer:
A projectile motion involves two components of motion -- vertical and horizontal. Characteristically,
motion in one direction is independent of motion in another direction.
Question:
10. A projectile is
Answer:
an object that moves in two dimensions under the influence of gravity and nothing else.
