introduction to projectile motion mr. chin-sung lin
TRANSCRIPT
Introduction to
Projectile Motion
Mr. Chin-Sung Lin
Introduction to Projectile Motion
What is Projectile Motion?
Trajectory of a Projectile
Calculation of Projectile Motion
Introduction to Projectile Motion
What is Projectile Motion?
Trajectory of a Projectile
Calculation of Projectile Motion
What is Projectile Motion?
Features of Projectile Motion?
2-D Motion
Parabolic Path
Affected by Gravity
Thrown into the Air
Determined by Initial Velocity
Definition: Projectile Motion
Projectile motion refers to the 2-D motion of
an object that is given an initial velocity and
projected into the air at an angle.
The only force acting upon the object is
gravity. It follows a parabolic path
determined by the effect of the initial
velocity and gravitational acceleration.
Definition: Projectile Motion
Projectile motion refers to the 2-D motion of
an object that is given an initial velocity and
projected into the air at an angle.
The only force acting upon the object is
gravity. It follows a parabolic path
determined by the effect of the initial
velocity and gravitational acceleration.
Introduction to Projectile Motion
What is Projectile Motion?
Trajectory of a Projectile
Calculation of Projectile Motion
Trajectory (Path) of a Projectile
Trajectory (Path) of a Projectile
v0
x
y
x
y
x
y
x
y
x
y
Velocity is changing and the motion is accelerated
The horizontal component of velocity (vx) is constant
Acceleration from the vertical component of velocity (vy)
Acceleration due to gravity is constant, and downward
a = - g = - 9.81m/s2
g = 9.81m/s2
x
y
The horizontal and vertical motions are independent of each other
Both motions share the same time (t)
The horizontal velocity ....vx = v0
The horizontal distance .... dx = vx t
The vertical velocity .... .... vy = - g t
The vertical distance .... .... dy = 1/2 g t2
g = 9.81m/s2
Trajectory (Path) of a Projectile
The path of a projectile is the result of the simultaneous effect of the H & V components of its motion
V component accelerated downward motion
H component constant velocity motion
H & V motions are independent
H & V motions share the same time t
The projectile flight time t is determined by the V component of its motion
Trajectory (Path) of a Projectile
H velocity is constant vx = v0
V velocity is changing vy = - g t
H range: dx = v0 t
V distance: dy = 1/2 g t2
Introduction to Projectile Motion
What is Projectile Motion?
Trajectory of a Projectile
Calculation of Projectile Motion
Calculation of Projectile Motion
Example: A projectile was fired with initial velocity v0 horizontally from a cliff d meters above the ground. Calculate the horizontal range R of the projectile.
g
R
d
v0
t
Strategies of Solving Projectile Problems
H & V motions can be calculated independently H & V kinematics equations share the same
variable t
g
R
d
v0
t
Strategies of Solving Projectile Problems
H motion: dx = vx t R = v0 t
V motion: dy = d = 1/2 g t2 t = sqrt(2d/g)
So, R = v0 t = v0 * sqrt(2d/g)
g
R
d
v0
t
Numerical Example of Projectile Motion
H motion: dx = vx t R = v0 t = 10 t
V motion: dy = d = 1/2 g t2 t = sqrt(2 *19.62/9.81) = 2 s
So, R = v0 t = v0 * sqrt(2d/g) = 10 * 2 = 20 m
g = 9.81 m/s2
R
19.62 m
V0 = 10 m/s
t
Exercise 1: Projectile Problem
A projectile was fired with initial velocity 10 m/s horizontally from a cliff. If the horizontal range of the projectile is 20 m, calculate the height d of the cliff.
g = 9.81 m/s2
20 m
d
V0 = 10 m/s
t
Exercise 1: Projectile Problem
H motion: dx = vx t 20 = v0 t = 10 t t = 2 s
V motion: dy = d = 1/2 g t2 = 1/2 (9.81) 22 = 19.62 m
So, d = 19.62 m
g = 9.81 m/s2
20 m
d
V0 = 10 m/s
t
Exercise 2: Projectile Problem
A projectile was fired horizontally from a cliff 19.62 m above the ground. If the horizontal range of the projectile is 20 m, calculate the initial velocity v0 of the projectile.
g = 9.81 m/s2
20 m
19.62 m
V0
t
Exercise 2: Projectile Problem
H motion: dx = vx t 20 = v0 t
V motion: dy = d = 1/2 g t2 t = sqrt(2 *19.62/9.81) = 2 s
So, 20 = v0 t = 2 v0 v0 = 20/2 = 10 m/s
g = 9.81 m/s2
20 m
19.62 m
V0
t
Summary of Projectile Motion
What is Projectile Motion?
Trajectory of a Projectile
Calculation of Projectile Motion
Projectile Motion with Angles
Mr. Chin-Sung Lin
Example: Projectile Problem – H & V
A projectile was fired from ground with 20 m/s initial velocity at 60-degree angle. What’s the horizontal and vertical components of the initial velocity?
g = 9.81 m/s2
20 m/s
60o
vx
vy
Example: Projectile Problem – At the Top
A projectile was fired from ground with 20 m/s initial velocity at 60-degree angle. What’s the velocity of the projectile at the top of its trajectory?
g = 9.81 m/s2
R
v
t
20 m/s
60o
vy
vx
Example: Projectile Problem – Height
A projectile was fired from ground with 20 m/s initial velocity at 60-degree angle. What’s the maximum height that the ball can reach?
g = 9.81 m/s2
h
20 m/s
60o
vy
vx
Example: Projectile Problem - Time
A projectile was fired from ground with 20 m/s initial velocity at 60-degree angle. How long will the ball travel before hitting the ground?
g = 9.81 m/s2
t
20 m/s
60o
vy
vx
Example: Projectile Problem – H Range
A projectile was fired from ground with 20 m/s initial velocity at 60-degree angle. How far will the ball reach horizontally?
g = 9.81 m/s2
R
20 m/s
60o
vy
vx
Example: Projectile Problem – Final V
A projectile was fired from ground with 20 m/s initial velocity at 60-degree angle. What’s the final velocity of the projectile right before hitting the ground?
g = 9.81 m/s2
20 m/s
60o
vy
vx
vfx
vfy vf
Example: Projectile Problem – Max R
A projectile was fired from ground with 20 m/s initial velocity. How can the projectile reach the maximum horizontal range? What’s the maximum horizontal range it can reach?
g = 9.81 m/s2
R
20 m/s