Phys 1112
Homework #2 Solutions
#2.90 [Cliff Height]
(a)
Time taken for rock to reach ground is tR =
2H
g , where H is the height of the
cliff.
H
Time taken for sound to reach top again tS = v , where vS = speed of sound
S
Total time from dropping rock to
Physics 1112
Homework #1
References:
Chapter 1, sections 1.1 - 1.10 (through Example 1.11 on page 22)
Chapter 3, section 3.5
Physics Ideas:
Math Skills:
Fall 2012
Physical quantities, precision, units
Average & instantaneous speed
Average and instantaneou
Phys 1112
Homework #8
Short Answers
#8.12 Fx = 8800 N, Fy = 2690 N
#8.19 (a) 6.79 m/s
(b) 55.2 J
#8.72 (a) 5.00 m/s (b) 5.71 m/s
(e) 5.38 m/s, 21.8o N of W
#1
(a) v0/2
(c) 0.27, 0.73
(c) 3.78 m/s
(d) 5.38 m/s, 21.8o N of E
(b)
#8.83 (a) 2.60 m/s
(b) 325
Phys 1112
Homework #7 Solutions
#6.57 [Ski Tow Power]
L
o
The tow is pulling N = 50 skiers up a 15.0 slope.
Each skier has a mass of 70 kg. The length of the
slope is 300 m and the speed of the tow is
v
M
km 10 m
1h
v 12
3.33m / s . We can
h 1km 3600s
fi
Phys 1112
Homework #6 Solutions
#6.38 [Leg Presses]
The work done is 80.0 J for a compression of x = 0.200 m.
1
2W
N
Then, since W k (x) 2 , k
4 103 .
F
2
2
(x)
m
(a) When compressed 0.200 m, the force exerted on the
N
spring is F kx 4 103 0.200m 800 N
Phys 1112
Homework #5 Solutions
#5.40 [Baseball with Air Drag] To find the terminal speed of the baseball, consider the freebody diagram:
+
FD
a
The terminal speed is the speed at which the drag
force equals the force of gravity (the weight) and
therefore
Phys 1112
Homework #4 Solutions
y
F1=100 N
#4.37 [Pushing a Cart]
60 o
(a) In order for the cart to move along the x direction
the total force in the y direction must be zero: Fy 0.
Then F1 sin 60o F2 sin 30o F3 y 0 and
x
30
F3 y 17 N .
o
F2=140 N
If F3 h
Phys 1112
Homework #3 Solutions
#3.29 [Ferris Wheel]
Assume counterclockwise motion. R = 14.0 m, vrim = 7.00 m/s. Find the magnitude and
direction of the acceleration at:
v2
3.5 m / s 2 toward the center of the wheel; upward
(a) the lowest point: a
R
(b
Physics 1112
Homework #1 Solutions
#1.15
[Precision & Significant Digits]
7
365.24 days 24 hr 3600 s
1 yr = 1 yr
day hr = 3.1557 10 s
yr
and
= 3.1416
3.1557 10 7 s 3.1416 10 7 s
= 0.00447 = 0.447%
3.1557 10 7 s
[NOTE: Our calculation starts with 5 sign
ECON 3130: Intermediate Microeconomics
Spring 2012
Solutions to the First Prelim
1.
a.
lobsters
b.
x2
noodle
c.
Organic strawberries
The dashed line is the budget line
x1
2. a. U(x,y) = (x1/2) + y
MUx = (x-1/2) , MUy = 1, MRS = MUx / MUy = (x-1/2)
b. Lagr
To be worked & discussed on Wed.-Thur., Oct. 10-11 at your Discussion class, as well as
turned in to your Discussion instructor's HW box by 4 PM on Friday, Oct. 12:
#4. [Meteors] Our goal here is to estimate the maximum and minimum speeds of meteors
reach
Homework #6
Physics 1112
References:
Chap. 6, sections intro., 6.1-3; Chap. 7, sections intro., 7.1-3
Physics Ideas:
Math Skills:
Fall 2012
Work & Kinetic Energy
Work-Energy Theorem
Conservative forces & Potential Energy
Conservation of Energy
Geometry, T
Homework #2
Physics 1112
References:
Physics Ideas:
Math Skills:
Fall 2012
Chapter 2 (all); Chapter 3, intro., sections 3.1-3.3
Position & displacement in 1 & 2-D
Average & instantaneous velocity & acceleration in 1 & 2-D
Motion in 1-D with constant or no