Diploma sem 2 applied science physics-unit 4-chap-1 projectile motion

PROJECTILE MOTION
Course: Diploma
Subject: Applied Science Physics
Unit: IV
Chapter: I

Projectile motion
 Projectile is a body thrown with an initial velocity
in the vertical plane and then it moves in two
dimensions under the action of gravity alone
without being propelled by any engine or fuel. Its
motion is called projectile motion.
 The path of a projectile is called its trajectory.

Examples:
1. A packet released from an airplane in
flight.
2. A golf ball in flight.
3. A bullet fired from a rifle.
4. A jet of water from a hole near the
bottom of a water tank.

 If gravity were not present, a projectile would
travel in a constant straight line.
 However, the presence of gravity forces
projectiles to travel in a parabolic trajectory,
thus gravity accelerates objects downwards.
 The factors that affect the trajectory are:
 a) Angle of projection
 b) Projection velocity
 c) Relative height of projection

Projection speed
Projection height
Projection angle
Factors Affecting the Trajectory of a Projectile

Optimum Projectile Angle or Angle of
projection
 The angle at the projectile body is thrown
is called Optimum Projectile Angle or
Angle of projection

Optimum Projectile Angle or Angle of
projection
 If Relative Projection Height = 0, the optimum
angle = 450
 If Relative Projection Height > 0 , the optimum
angle < 450
 If Relative Projection Height < 0 , the optimum
angle > 450

The time of flight
 The time of flight of a projectile motion is
the time from when the object is projected
to the time it reaches the surface. As we
discussed previously, T depends on the
initial velocity magnitude and the angle of
the projectile:
yu
T
g
u sin
T
g

 


Maximum height
 maximum height, which is the height of
the projectile when the vertical velocity is
zero and the projectile has only its
horizontal-velocity component.
2
y
2
max
max
y
2 2 2 2
2
2 2
u sin
T & u usin
g
2u sin
g
u sin
1
X u t at
2
X h &a g & t
usin 1
h u
u
sin g
g 2
1
h g
2
h
sin
g g
u sin
2g
 
  
   
      
   
   
     

 
  
 

  
 
   

  




Horizontal range
 The range, R, which is the horizontal distance
that the projectile travels.
Range R
Range is the total horizontal
distance covered during the
time of flight.
From equation for horizontal
motion, x=uxt
When t=T , x=R
R= uxT = ucos.2usinΦ/g
= u22sinΦcosΦ/g =
u2sin2Φ/g using 2sinΦcosΦ=
sin2Φ
R= (u2sin2Φ)/g

Equation of Trajectory (Path of projectile)
 At any instant t
x= u.cosΦ.t
t= x/(u.cosΦ)
 Also , y= u sinΦ.t - (1/2)gt2
 Substituting for t
y= u.sinΦ.x/(u.cosΦ) - (1/2)g[x/(u.cosΦ)]2
 y= x.tanΦ - [(1/2)g.sec2.x2 ]/u2
 This equation is of the form y= ax + bx2 where 'a'
and 'b are constants. This is the equation of a
parabola.
 Thus, the path of a projectile is a parabola .

A lava rock is thrown horizontally at 15m/s from
the top of a cliff 44 m high.
a. How far form the base of the cliff does the
rock hit the ground?
KNOWN:
xy = -44 m xx =?
ay= -9.8 m/s/s ax = 0
vi,y = 0 vi,x = 15m/s
vf,x = 0

First we need to solve for the time.
Use the formula xy = vit + 1/2at2
Time = 3 seconds
Now we know the time and we can find how far
from the base of the cliff it landed.
Use the formula v= x/t and
the distance is 45 m

 The movie “The Gods Must Be
Crazy” begins with a pilot dropping
a bottle out of an airplane.
 It is recovered by a surprised
native below, who thinks it is a
message from the gods.
 If the plane was flying at an altitude
of 500 m, and the bottle lands 400
m horizontally from the initial
dropping point, how fast was the
plane flying.

 An autographed baseball rolls off of a 0.70m
high desk and strikes the floor 0.25 m away
from the base of the desk. How fast was it
rolling?
 A. 0.77 m/s
 B. 0.66 m/s
 C. 0.54 m/s

Answer : A
A projectile is…
A. An object thrown or launched
into the air.
B. An object rolling down a hill
C. An object that is being hit by a
bat or other object

A cat chases a mouse across a 1.0 m
high table. The mouse steps out
of the way, and the cat slides
off the table and strikes the
floor 2.2m from the edge of the
table. What was the cat’s speed
when it slid off the table?
A. 5.9 m/s
B. 2.4 m/s
C. 4.9 m/s

A pelican flying along a horizontal
path drops a fish from a height of
5.4 m. The fish travels 8.0 m
horizontally before it hits the
water below. What is the
pelican’s initial speed?
A. 5.4 m/s
B. 7.7 m/s
C. 9.8 m/s

The path a projectile takes is
called_________
A. Parabola
B. Trajectory
C. equilibrium

 During a thunderstorm, a tornado lifts a cow to a
height of 125 above the ground. Increasing in
strength, the tornado flings the cow horizontally
with an initial speed of 90 m/s. How long does
the cow take to reach the ground? How far does
the cow travel before hitting the ground?
 A. 5.05 s ; 454m
 B 5.05 s ; 234 m
 C. 4.03 s ; 454 m
 D. 4.03 s ; 454 m

 A ball is thrown horizontally
from the top of a building
from a height of 32.5 meters
above the ground. It lands 56
meters from the base of the
building. What is the initial
velocity of the ball? ( Two
significant digits)

Answer : C
In the x direction (ignoring air resistance),
the force acting on the projectile is________
A. The force that launched
B. Gravity
C. There are no forces in the x direction

Answer : A
In the x direction (ignoring air resistance),
the acceleration of the projectile is____
A. Zero
B. 9.8 m/s
C. Increasing by 9.8 m/s every second.

Answer : c
In the x direction
(ignoring air
resistance), the velocity
of a projectile______
A. Increases
B.
Decreases
C. Stays the
same

In the x direction, the object’s speed
______. (Ignoring air resistance)
A. Increases
B. Decreases
C. Stays the same

Answer : A
A projectile is an object that the only forces
acting on it are air resistance and
gravity.
A. True
B. False

Answer: B
If an object is shot horizontally, the initial
velocity in the y direction is_____________
A. 9.8 m/s
B. Zero
C. Dependent on the time

 The organs fly off the edge of a table with a
velocity of ____m/s. The height of the table is 3
m and the horizontal range of the organs from
the base of the table is 15 m. How long does it
take for the organs to hit the ground?
 A. .61s
 B. 9.8 s
 C. .78 s
 D. .57 s

Answer : 145.5 m
A bridge is 180 m above a river. If a
goat is thrown from the bridge by a
troll with a horizontal velocity of 24
m/s. How far has the goat moved
horizontally when it hits the water?

 A ball rolls off the edge of a table with a
horizontal velocity of ___ m/s. The height of
the table is 7 m and the horizontal range of the
ball from the base of the table is 15 m. What is
the initial speed of the ball.
 A. 35 m/s
 B. 24 m./s
 C. 32 m/s
 D. 13 m/s

Zeus throws a lightning bolt with a
horizontal velocity of 25 m/s. The
lightning bolt lands 30 meters away
from the cloud. How high is the
cloud?

A ball is launched with an
initial velocity of 4.47
m/s at an angle of 66
degrees with the
horizontal.
a. What was the
maximum height the
ball attained?
b. How long did it take
the ball to return to the
launching height?
c. What was its range?
0.86 m
0.84 s
1.5 meters

 A rugby player kicks a
ball from ground level
with an initial velocity
of 27.0 m/s at 30
degrees above the
horizontal.
 What is the….
 A. Hang time
 B. range
 C. Maximum height
2.76 s
64.6 m
9.3 m

A can is kicked with an initial speed of 60 m/s
at an angle of 30 degrees above the
horizontal. What s the can’s horizontal
displacement at the end of 4 seconds?

Answer : C
 A baseball is hit with a vertical speed of 20
m/s and a horizontal speed of 30 m/s. How
long will the ball remain in the air?
 A. 2 seconds
 B. 3 seconds
 C. 4 seconds
 D. there is no way to tell

A girl kicks a robot and the head flies off at
an angle of 20 degrees. The head would
have landed at the same spot if it had been
kicked at an angle of:
A: 40 degrees
b. 70 degrees
C. 45 Degrees
D. 25 degrees

The horizontal and
vertical components
of the initial velocity
of a football are 24
m/s and 7 m/s
respectively. What
is the initial velocity
of the football?

A bride throws a
bouquet with an
initial velocity of 27
m/s at an angle of 25
degrees above the
horizontal. How high
above the projection
point is the bouquet
after 1.8 s?

Answer : C
A ball is thrown at an angle of 45
degrees above the horizontal
with an initial velocity of
20m/s. What is the total time
of flight of the ball before it
hits the ground?
A. 9.8 s
B. 6.1 s
C. 2.9 s
D. 4.9 s

Answer : D
 A man kicks a soccer ball with an initial
velocity of 25 m/s at an angle of 30°above
the horizontal. The horizontal component of
the velocity of the ball is described by one
of the following statements.
 A) It changes uniformly.
 B) It is zero.
 C) It is 25 m/s.
 D) It remains constant during the ball's
flight.

Answer : C
 A man is launched from a cannon
with an initial velocity of 26 m/s at
an angle of 20 degrees above the
horizontal. How high above the
projection point is the man after 1.4
s?
 A. 8.2 m
 B. 24 m
 C. 2.8 m

 Suppose that an angel flying
60 m/s, at a height of 300m,
dropped a sack of halos.
How far from the point of
release would the sack have
traveled when it struck the
ground?

 A snowball is thrown at some
angle above the horizontal with a
certain velocity. It reaches its
highest point and starts falling
down. What is the velocity of the
snowball at the highest point of
the trajectory?
 A. 9.8 m/s
 B. It is equal to its initial
horizontal velocity
 C. 0
 D. It is equal to its initial vertical
velocity.
Answer : B

Answer : A
Which of the following conditions is met when a
projectile reaches its maximum height?
A. Vertical component of the velocity is zero.
B. Vertical component of the velocity is maximum.
C. Horizontal component of the velocity is
maximum.
D. Acceleration in the vertical direction is zero.

Answer : C
What is the range of a projectile?
A. The total trajectory that the projectile travels.
B. The vertical distance that the projectile travels.
C. The horizontal distance that the object travels.
D. Twice the maximum height of the projectile.

Answer : B
 The horizontal and vertical
components of the initial
velocity of a soccer ball are
24m/s and 7 m/s
respectively. What is the
initial velocity of the soccer
ball?
 A) 31 m/s
 B) 25 m/s
 C) 17 m/s
 D) 42 m/s

Define the flight time or hang time of a trajectory.
A. Time taken by the projectile to reach the
maximum height.
B. The maximum height reached by the projectile
divided by the magnitude of the vertical velocity.
C. The total time the projectile was in the air.
D. Half the total time the projectile was in the air.

Answer : B
. What is the maximum
height obtained by a
125g rock that is slung
from a slingshot at an
angle of 78° from the
horizontal with an
initial velocity of 18
m/s?
A. 0.70 m
B. 16 m
C. 32 m
D. 33 m

An orange is dropped at the same time a bullet is
shot from a gun ( ignoring air resistance). Which
of the following is true?
A. The acceleration due to gravity is greater for the
orange because the orange is heavier.
B. Gravity acts less on the bullet than on the orange
because the bullet is moving so fast.
C. The velocities will be the same.
D. The two objects will hit the ground at the same
time.

 A baseball player throws a ball from left field
toward the home plate. ( Neglecting air resistance)
At the instance the ball reaches its highest point,
what is the direction of the ball’s velocity?
 A. Up
 B. Down
 C. horizontal
 D. There is not enough information to say

If an object is shot upward at an angle (no air) and
lands at the same height it is shot, the final velocity
is
A. Zero
B. The same as the initial velocity
C. Negative the initial velocity

REFERENCE BOOKS AUTHOR/PUBLICATION
ENGINEERING PHYSICS
B.L.THERAJA, S. CHAND
PUBLISHERS

1. http://exbiomech.tamu.edu/afp_hlknwebsrv
.tamu.edu/KINE_426_files/11.PROJ.K426a
.pptx
2. http://images.tutorvista.com/content/gravita
tion/projectile-flight-time.gif
3. http://3.bp.blogspot.com/_teko96dlZB4/TN
bFs9tF4qI/AAAAAAAAACc/1JTTisEAqc
M/s1600/projectile_motion_picture.jpg
4. https://figures.boundless.com/16970/full/ra
nge.gif
5. http://dallaswinwin.com/Motion_in_Two_
Dimensions/projec1.gif

Diploma sem 2 applied science physics-unit 4-chap-1 projectile motion

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Diploma sem 2 applied science physics-unit 4-chap-1 projectile motion