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Midterm

Hawaii PHYS 151 exam151m2-07sprExam


Department
Physics
Course Code
PHYS 151
Professor
All
Study Guide
Midterm

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Physics 151 Roster No.:
Due: Friday, March 23, 2007
Score:
Take-Home Midterm Exam #2, Part A
NO exam time limit. Calculator required. All books and notes are allowed, and you may obtain help
from others. Complete all of Part A AND Part B.
You do NOT need to show your work for fill-in-the-blank and multiple-choice questions. For multiple-choice
questions, circle the letter of the one best answer (unless more than one answer is asked for). For all fill-in-the-
blank answers, be sure to provide proper units and significant figures!
Show your work on all free-response questions. Be sure to use proper units and significant figures in your
final answers.
Ignore friction and air resistance in all problems, unless told otherwise.
Physical constants: It’s an open-book test, so you can look them up in your textbook!
Useful conversions: It’s an open-book test, so you can look them up in your textbook!
1. (4 pts.) Convert the following quantities into the given units. Fill in the blanks. (You do NOT need to show
your work.) Use scientific notation where appropriate (very large or very small values). Express all final values to
THREE significant figures.
a. 433 MHz = GHz
b. 3.00 × 1010 cm/s = AU/min (1 AU = average Earth–Sun distance = 1.50 × 108 km)
c. 7850 rpm = rad/ms (“rpm” = rev/min)
d. 875 MJ = kW·h (“h” = hour)
2. In a particular park, children can choose from three different FRICTIONLESS slides, as shown above. All three
start and end at the same vertical positions. Assume that all children start from rest at the top of any slide.
a. (1 pt.) If a heavy child and a lightweight child both descend the same slide, which one will be TRUE?
A. The heavier child will reach the bottom with greater speed and shorter time.
B. The heavier child will reach the bottom with greater speed, but equal time.
C. The heavier child will reach the bottom with equal speed, but shorter time.
D. The heavier child will reach the bottom with equal speed and equal time as the lightweight child.
b. (1 pt.) If the same child descends each slide in turn, which slide will give her the greatest final speed?
A. slide A B. all slides are equal C. slide C D. not enough information given
c. (1 pt.) If the same child descends each slide in turn, which slide will give her the fastest time of descent?
A. slide A B. all slides are equal C. slide C D. not enough information given
slide A
slide B
slide C

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3. (5 pts.) The mass M = 125 kg hangs at rest as shown above, suspended by three massless cables. The cables are
joined at the center, and cable #3 hangs straight down.
a. What is the magnitude of tension FT1? ____________________
b. What is the magnitude of tension FT2? ____________________
c. What is the magnitude of tension FT3? ____________________
4. (6 pts.) A heavy rail car (m = 1500 kg) rolls on the ground on rails, and is constrained so that it can only move to
the right or left, as shown in the top-view above. Three people supply constant forces by pulling on cables attached
to the car’s center. (Assume that the three forces do NOT change magnitude or direction as the car moves.) The car
starts from rest, and there is no friction. When the car has moved 12.0 m to the right, what is…
a. the work done on the car by FT1? ____________________
b. the work done on the car by FT2? ____________________
c. the work done on the car by FT3? ____________________
d. the final speed of the car? ____________________
FT1
FT2
FT3
M
40.0˚
110.0˚
FT1 = 375 N
FT2 = 380. N
12.0 m
25.0˚
55.0˚
90.0˚
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