Transcript Horizontal_Projectile_Motion

Horizontal Projectile
Motion
By
Lisa Levenson
Katya Fatakhova
Kaitlin Magee
Daniel Wittenberg
Horizontal Projectile Motion
• An object fired or thrown
horizontally
• The vertical velocity of the object is
always 0.
• The object falls to the ground
vertically, and maintains an
acceleration of 9.81 m/s2 (Like in Free
Fall)
Break Packet #31-Horizontal Projectile
Motion
A 0.2-kilogram red ball is thrown horizontally at a speed of 4
meters per second from a height of 3 meters. A 0.4-kilogram
green ball is thrown horizontally from the same height at a
speed of a 8 meters per second. Compared to the time it
takes the red ball to reach the ground, the time it takes the
green ball to reach the ground is
A) twice as great
B) the same
C) four times as great
D) one-half as great
ANSWER!!!!
A 0.2-kilogram red ball is thrown horizontally at a speed of 4
meters per second from a height of 3 meters. A 0.4-kilogram
green ball is thrown horizontally from the same height at a
speed of a 8 meters per second. Compared to the time it
takes the red ball to reach the ground, the time it takes the
green ball to reach the ground is
A) twice as great
B) the same
C) four times as great
D) one-half as great
EXPLANATION
This problem can be solved through the
equation:
dy = vi(t)+(1/2)at2
vi = 0, so that part of the equation can be
eliminated.
t = √(2d/a)
Therefore (neglecting air resistance), the only
factors that affect the time of the object's fall
is its distance from the ground and its
acceleration, both of which are the same for
the two objects in this problem.
A ball is thrown horizontally with an initial velocity of 20
meters per second from the top of a tower 60 meters high.
What is the horizontal velocity of the ball just before it
reaches the ground? [Neglect air resistance.]
(A) 34.3 m/s
(B) 20.0 m/s
(C) 68.6 m/s
(D) 9.81 m/s
A ball is thrown horizontally with an initial velocity of 20
meters per second from the top of a tower 60 meters high.
What is the horizontal velocity of the ball just before it
reaches the ground? [Neglect air resistance.]
(A) 34.3 m/s
(B) 20.0 m/s
(C) 68.6 m/s
(D) 9.81 m/s
ANSWER EXPLAINED
The answer would be equivalent to the initial velocity. The
horizontal velocity does not change when the ball is thrown in
the air.
Neglecting air resistance, there is no horizontal acceleration,
and therefore the horizontal velocity remains constant.
Newton's First Law:
An object in motion tends to stay in motion(at a constant
velocity), unless acted upon by an outside force.
Review - Short Answer
An airplane flying horizontally at 150m/s drops a bomb from a
height of 2500m. How far in front of the target must the
bomb be released?
This problem must be solved in two steps:
1) Find the time it takes for the bomb to hit the ground
dy = viy + (1/2)at2
(The initial y velocity is 0.)
2,500m = (1/2)(9.81m/s2)t2
2,500m = 4.9m/s2(t)2
2,500m/4.9m/s2 = t2
t = √(510s2)
t = 23s
Review - Short Answer (continued)
2) Find the range (using t)
dx= vit + (1/2)at2
(In this case velocity is constant, and so there is no acceleration)
dx = vit
dx=(150m/s)(23s)
dx= 3.5 x 103m
The bomb must be released 3.5 x 103m in front of the target.
ANGRY BIRDS PROJECTILE ANIMATION
http://www.youtube.com/watch?v=vfWgzQHX9Fg&feature=re
lated
In this game, in order to kill the pigs, one must find the
proper angle to shoot the "angry birds." This shows projectile
motion, and also demonstrates the idea that at different
angles, an object has varied flight time, and flight distance.
HOMEWORK
Homework will be given out on a worksheet in class.