Department

PhysicsCourse Code

PHYS 151Professor

AllStudy Guide

MidtermThis

**preview**shows pages 1-2. to view the full**7 pages of the document.**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

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

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

FT3 = 430. N

12.0 m

25.0˚

55.0˚

90.0˚

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