This preview shows pages 1–2. Sign up to view the full content.
1
Chap4HW1 Questions
7.
An airplane flying horizontally at a constant speed of 350 km/h over level ground
releases a bundle of food supplies. Ignore the effect of the air on the bundle.
What are the bundle's initial (a) vertical and (b) horizontal components of velocity?
a)
v
oy
= 0 km/h,
b)
v
ox
= 350 km/h,
(c) What is its horizontal component of velocity just before hitting the ground?
There is no significant horizontal acceleration so
v
x
= 350 km/h,
(d) If the airplane's speed were, instead, 450 km/h, would the time of fall be longer, shorter,
or the same?
Same.
Time of fall is determined by vertical acceleration and vertical initial velocity
9.
Three paths are shown for a football kicked from
ground level.
Ignoring the effects of air, rank the paths
according to
(a) time of flight,
Since they all rise to the same height, they all tie;
(b) initial vertical velocity component,
Since they all rise to the same height all tie
(c) initial horizontal velocity component
They have different horizontal initial velocities
because their ranges are different:
3, 2, 1;
(d) initial speed, greatest first:
3, 2, 1
Problems
17.
A projectile is fired horizontally from a gun that is 45.0 m above flat ground, emerging
from the gun with a speed of 250 m/s.
(a) How long does the projectile remain in the air?
Know that
2
0
2
1
at
t
v
y
y
oy
+
+
=
Choose origin at initial position of ball so
y
o
= 0
and
y
= 45 m
Since the ball is fired horizontally
0
=
oy
v
Therefore
()
s
03
.
3
m/s
9.8

m
45
2
2
2
=
−
×
=
=
a
y
t
(b) At what horizontal distance from the firing point does it strike the ground?
Since there is no horizontal acceleration,
t
v
x
x
ox
=
−
0
= 758 m
(c) What is the magnitude of the vertical component of its velocity as it strikes the ground?
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 oshea

Click to edit the document details