Physics 201/211: Test 1

9:30AM Thursday, September 12, 1996

NAME (printed):

Student Number (SSN):

Recitation Section Number :

INSTRUCTIONS:

• Wait for the oral instruction to begin.
• Show all your work in order to qualify for partial credit. Write legibly!
• Assist the graders by placing a box around your final answer.
• You may only use your calculator for simple arithmetic operations.

You may find the following data useful:

, downward.

Note the formula sheet appended to the end of the test.

This test is worth 50 points. Good Luck!

: Multiple Choice. Circle the most suitable answer for each of the questions enumerated below. There is no partial credit for this section. Each question is worth 3 points.

1. Consider the weight on the air track we saw in class. When the weight hits the bumper at the end of the track, it slows down and comes to a stop before reversing its direction. What is its acceleration at the moment its velocity is zero? (Define its initial direction of motion as ``positive''.)

a)

zero

b)

infinity

c)

nonzero and positive

d)

nonzero and negative

2. Claiborne Farm's Secretariat won the 1973 Belmont Stakes in a world record time of 2:24 for the 1.50 mile distance. What was his average speed in miles per hour?

a)

-22.3 miles/h

b)

37.5 miles/h

c)

48.2 miles/h

d)

27.3 miles/h

3. Suppose you wanted to plot the acceleration of an object with time from a plot of its position with time. Which of the following is true?

a)

You have to plot the slope of the position curve's slope with time.

b)

You have to plot the average velocity divided by the time elapsed.

c)

You have to plot the slope of the position curve with time.

d)

It is not possible to determine the acceleration in this way.

4. A boy throws a ball up into the air with an initial speed of 3.0 m/s. How much time will elapse before the ball reaches its highest point?

a)

.31 s

b)

.62 s

c)

.12 s

d)

.84 s

{5. For problem #4, what can you say about the velocity of the ball when it returns to the level of his hand?

a)

The velocity is given by -g.

b)

The velocity is zero.

c)

It has the same speed as it did originally, and the velocity is in the same direction.

d)

It has the same speed as it did originally, but the velocity is in the opposite direction.

: Short Answer. State your answer briefly, in coherent sentences. This section is worth 5 points.

6. Some two millenia ago, Aristotle wrote a treatise asserting that heavier objects fall faster. Recalling the demonstrations shown in class, explain how you would convince Aristotle that he is wrong. (Hint: There were no vacuum pumps in ancient Greece!)

: Problems. Show your work completely to obtain at least partial credit. Read each problem carefully! Each problem is worth 10 points.

7. The road runner is running through cartoon land at an initial velocity of 27 km/h when a cliff suddenly appears in his path. He skids to a stop in the nick of time, leaving skidmarks 53 meters long. What was his acceleration? (Here we insist that cartoon characters obey physical law.)

true in

8. A car speeding at a constant velocity of 123 km/h passes a stationary police car. The police car immediately gives pursuit and catches up with the speeder 53.4 s later. What was the police car's acceleration?
 
 

9. Consider the following plot of an object's velocity versus time. For each of the following questions, write the letter(s) of the points which answer that question.

a)

At which point(s) is the speed greatest?

b)

At which point(s) is the acceleration zero?

c)

At which point(s) is both the velocity and acceleration zero?

d)

At which point(s) is the acceleration in a direction opposite to the velocity?

e)

At which point(s) is the acceleration in the same direction as the velocity?

(N.B. If something is zero, it can't have a direction.)

 

 
Thu Jan 30 14:47:12 EST 1997