NAME:

ID #:

Recitation Section #:

PH2100EXAM 1Summer 2002

INSTRUCTIONS

  1. Please write your name, student identification number and recitation section on the space provided above, and also on the TOP OF EVERY PAGE OF THIS EXAM.
  2. With the exception of the included fresh equation sheet, no other equation sheets, papers, books, handbooks or tables are permitted.
  3. No materials, including calculators, may be exchanged during the exam.
  4. Keep your eyes on your own papers.
  5. Units are an important part of numerical answers; be sure to include units on your answers.
  6. Report all numerical answers to three significant figures unless the problem specifically instructs otherwise.
  7. Vectors should be reported using unit-vector notation, unless otherwise instructed.
  8. All answers are worth 5 points each, unless marked otherwise.
  9. There are a total of 100 possible points on the exam.

Recitation SectionInstructor

R01Jason Wang

R02Vijaya Kayastha

Raw Score:

Redemption:

Total Score:

Name:

PH2100Exam I 6/12/2002

PROBLEMS

  1. A farmer wants to calculate the perimeter of a newly purchased field to build a fence for next year. The shape of the field and some corresponding dimensions are shown in the figure. Following the rules for significant figures, calculate the perimeter of the farmer’s field. Give your answer in meters and use proper scientific notation for full credit.
  1. In a preliminary field test, a new car was observed to travel such that its displacement in one dimension as a function of time was given by the expression:

x(t) = 2.29 t2 + 0.556 t3

where, x is in meters, t is in seconds.

(a)Find the instantaneous acceleration of the car at time t = 2.50 s.

(b)Find the average speed of the car during the first 2.50 s.

  1. A stone is thrown straight upward from the top of a tall building by a person standing hear the edge of the roof. The initial speed was 20.0 m/s. If the stone hits the ground with a velocity 37.1 m/s downward, how tall was the building?
  1. A quarterback throws a football toward a receiver with an initial speed of 19.5m/s at an angle 30.0º above the horizontal. At the instant the ball is thrown, the receiver is 21.0 m from the quarterback. In what direction (toward or away from the quarterback) and with what constant speed must the receiver run to catch the football at the same level at which it was thrown? (10 pts)
  1. An ball swings counter clockwise in a vertical circle at the end of a rope 1.50 m long. When the ball is 36.9º past the lowest point and on its way up, its total acceleration is

(-22.5i + 20.2j) m/s2. For that instant:

(a)sketch a vector diagram showing the position

of the ball, the 36.9º angle, and components

of this acceleration.

(b)determine the speed of the ball. (10 pts)

(c)If the ball has a mass 0.267 kg, what is the magnitude of the force on the ball?

  1. The pilot of an airplane notes that the compass indicates a heading due west. The airplane’s speed relative to the air is 175 m/s. The velocity of the airplane relative to the ground is 195 m/s at 15.0º north of west. What is the velocity of the wind? (Hint: Draw a vector picture and use vector components. Give your answer using unit vector notation.) (10 pts)

MULTIPLE CHOICE circle the letter corresponding to the one best answer in each of the following (5 points each):

7.Suppose that two quantities A and B have different dimensions. Which of the following arithmetic operations could be physically meaningful?

(a)2A + 3B

(b)A2 / B

(c)B  A

(d)all of the above

(e)none of the above

8. Each of the graphs below shows position x as a function of time t for a different moving object. Which graph(s) show an object that is moving with a positive acceleration?

x x x x

t t

t t

graph I graph II graph III graph IV

(a) graph I, only

(b) graphs I and II, only

(c) graph I and IV, only

(d) graph I and III, only

(e) graph III and IV, only

9.Ball #1 is released from rest from the top of Fisher Hall. Ball #2 is projected horizontally from the same height as ball #1 with a non-zero initial speed. Neglecting the effects of air resistance, which ball has the higher speed as they hit the ground?

(a)They both hit the ground with the same speed.

(b)Ball #1.

(c)Ball #2.

10. If the speed of a mass is constant it cannot be accelerating.

(a)True

(b)False

11.A book is placed on a chair. Then a videocassette is placed on the book. The book exerts a normal force:

(a) on the floor, chair and videocassette.

(b) on the chair and the videocassette only.

(c) only on the videocassette.

(d) only on the chair.

(e) only on the objects that you have defined to be part of the system.

(f) on nothing because it is in equilibrium.

12.The apparent weight of a person in an elevator is smallest when the elevator:

(a) moves downward at constant velocity

(b) moves upward at constant velocity

(c) is not moving

(d) accelerates downward

(e) accelerates upward

13.Two children are pulling on a rope playing tug of war. Neither child is close to winning, and at the moment, the rope is not moving. At this moment, the force exerted by one child must be equal in magnitude and opposite in direction to the force exerted by the other child because:

(a) of Newton’s third law.

(b) the mass of the rope is negligible.

(c)the rope is not accelerating.

14. Three masses are placed on a table as shown in the diagram. A force F is acting on mass 1. Ignoring all friction forces, how many distinct forces are acting on mass 2?

(a) 0

(b) 2

(c) 3

(d) 4

(e) 5