PHYS170 - Intermediate General Physics I
Spring 2008

Answers to Some Even HW problems

Ch 1: Problem 8
67 mi/hr
Ch 1: Problem 10
a) 88 ft/sec
b) 9.8 m/sec2
c) 103 kg/m3
Ch 1: Problem 32
a) C= 9m, θ= 33.7o
b) C= 23.3m, θ= -109.7o
c) C= 9m, θ= -146.3o
d) C= 22.3m, θ= 70.3o
Ch 1: Problem 54
a) 14.0
b) 58.7o
Ch 2: Problem 12
a)
0 - 2 sec: aavg=0 m/s2
2 - 4 sec: aavg=1 m/s2
4 - 6 sec: aavg=2 m/s2
6 - 8 sec: aavg=2 m/s2
8 - 10 sec: aavg=3 m/s2
10 - 12 sec: aavg=1.5 m/s2
12 - 14 sec: aavg=1.5 m/s2
14 - 16 sec: aavg=0 m/s2
b)
At t=9 sec: a= 1.5 m/s2
At t=13 sec: a= 1.5 m/s2
At t=9 sec: a= 0 m/s2
Ch 2: Problem 14
(a) i) aavg= 1.7 m/s2
(a) ii) aavg= -1.7 m/s2
(a) iii) aavg= 0 m/s2
(a) iv) aavg= 0 m/s2
(b) At t=20 sec, a= 0 m/s2
(b) At t=35 sec, a= -1.7 m/s2
Ch 2: Problem 32
These are graphs you will hand in.
Ch 2: Problem 28
a) at 4.0 s, v = +2.7cm/s, at 7.0 s, v = -1.3cm/s,
b) from slope, a = -1.3 cm/s2
c) at 4.5 sec, x= 22.8 m, at 7.5 sec, x= 23.4 m
d) you're on your own
Ch 2: Problem 38
You will have to use your own reasonable estimates.
Ch 3: Problem 6
a) vx = 6.5 m/s, vy= 0.52 m/s
b) 4.6o above the horizontal
Ch 4: Problem 12
a) 4.31 m/s2
b) 215 m
c) 43 m/s
Ch 5: Problem 14
a) T1 = mBgsinα
b) T2 = mBgsinα + mAgsinα
c) NB = mBgcosα    NA = mAgcosα
d)
Ch 5: Problem 42
a) 19.3o
b) 0.92 m/s2
c) 3 m/s
Ch 6: Problem 8
-150J
Ch 6: Problem 8
-150 J
Ch 6: Problem 18
a) Wparallel=mgh, Wperpendicular=0
b) Wtotal = mgh = 1/2mv2
c) 17.1 sec
Ch 7: Problem 12
>
Ch 7: Problem 30
a) -59J
b) -42J
c) -59J
Ch 7: Problem 46
a) h > 5/2 R
b) 31.3 m/s, aradial= 49m/s2, atangential= 9.8m/s2 Ch 10: Problem 14
a) 42N
b) 11.8 m/s
Ch 10: Problem 40
a)
b) 7 rad/s
c) 1.03x10-2 J
d)
Ch 10: Problem 42
0.6 rev
Ch 12: Problem 50
a) 2.20x10-10 N, at θ=163o
b) x=0, y= 1.39m
Ch 13: Problem 44
2.6s
Ch 15: Problem 4
1.5x106 Hz
Ch 15: Problem 6
a) 6.5 mm
b) 28 cm
c) 27.8 Hz
d) 7.78 m/s
Ch 16: Problem 44
a) 0.798m
b) 0.922m
Ch 14: Problem 14
a) 2.52x106 Pa
b) 1.78x105 N
Ch 18: Problem 2
a) 983oC
b) 5.24x10-4 kg
Ch 18: Problem 14
a) 3.74
Ch 17: Problem 44
a) 30,000 J/kg
b) liquid: 1,000 J/kg C, solid: 1300 J/kg C
Ch 19: Problem 1
a)
b) 1.33x103 J
Ch 19: Problem 6
a)
b) -4.00x104 J
Ch 19: Problem 12
a) -1.15x105 J
b) -2.55x105 J