Your Name:  _______________________                              PHY203

                                                                                                            Exam #1

                                    Chapters 1-3

                                                                                                            Thurs, 9/30/10

 

 

 

Lecture Time:         9 a.m             1p.m.             2p.m.       3p.m.       Honors         

 

 

 

1-10    _________________        (out of 50)

 

 

 

11       _________________        (out of 20)

 

 

 

12       _________________        (out of 30)

 

 

 

Total              _______________

 

 

 

Multiple choice answer sheet-shade in correct answers below

(one choice per problem):

 

 

 

1

 

2

 

3

 

4

 

5

 

6

 

7

 

8

 

9

 

10

 

a

 

 

 

 

 

 

 

 

 

 

 

b

 

 

 

 

 

 

 

 

 

 

 

c

 

 

 

 

 

 

 

 

 

 

 

d

 

 

 

 

 

 

 

 

 

 

 

e

 

 

 

 

 

 

 

 

 

 

 

 

1. The world record in swimming for the 1500 m distance is 14 min., 35 sec. What was the average speed in miles per hour?

a.      0.064 mph

b.     3.84 mph

c.      9.90 mph

d.      38.4 mph

e.      None of the above

 

For questions 2-5, traveling in one direction, a train starts from rest with an acceleration of 5 m/s2 for 20 s. After 20 s, the train moves at constant speed for 50 s. Finally the train accelerates at -4 m/s2 until it comes to rest.

2.  Find the distance the train travels in the first 20 s.

a.      50 m

b.     100 m

c.      1000 m

d.      2000 m

e.      None of the above

 

3.  Find the speed of the train after 20 s.

a.      50 m/s

b.     100 m/s

c.      200 m/s

d.      1000 m/s

e.      None of the above

 

4.  Find the distance the train travels from 20 s to 70 s.

a.      2500 m

b.     5000 m

c.      10,000 m

d.      50,000 m

e.      None of the above

 

5.  Find the distance the train travels from 70 s until it comes to rest.

a.      12.5 m

b.     625 m

c.      1250 m

d.      2500 m

e.      None of the above

6.  A bike rider rides 3 km East and then 7.5 km North. Find the magnitude of the

displacement of the rider at the end of the trip.

a.      3.2 km

b.     4.5 km

c.      8.1 km

d.      10.5 km

e.      None of the above

 

7.  A bike rider rides 4.5 km East and then 8.0 km North. Find the angle the

displacement of the rider makes with respect to the East direction measured in a

counterclockwise direction from the positive East axis at the end of the trip.

a.      29.4 o

b.     40.4 o

c.      60.6 o

d.      64.6 o

e.      None of the above

 

For problems 8-10, on Planet XXX, the acceleration due to gravity is exactly 10 m/s2. Identical rocks are dropped from the top of a cliff. Find the time, t, at which the rocks are side-by-side.

 

8. Case1: Rock a is dropped at t = 0; rock b is dropped from the top of the cliff at t = 2 s.

a.           1.0 s

b.          2.0 s

c.           3.0 s

d.          4.0 s

e.          None of the above

 

9.  Case 2: Rock a is dropped at t = 0; rock b is thrown straight down at t = 2 s with an initial speed of 40 m/s.

a.           1.0 s

b.          1.67 s

c.           3.0 s

d.          5.0 s

e.      None of the above

 

10.  Case 3: Rock a is thrown down with an initial speed of 10 m/s at t = 0; rock b is thrown straight down at t = 2 with an initial speed of 40 m/s.

a.           1.2 s

b.          2.0 s

c.           6.0 s

d.          10.0 s

e.      None of the above

11.  First, fill in the plots above for v vs. t and a vs. t.

Show your work below:

a.  Find the total distance traveled from points B-H.

 

 

 

b.  Find the average speed from points B-H.

 

 

 

c.  Find the average velocity from points B-H.

 

 

d.  Find the displacement from points G-I.

 

 

 

e.  Find the instantaneous velocity at point H.

 

 

f.  Find the average acceleration from points C-H.


12.  A boy who is standing on top of a 30 m tall building throws a ball at a nearby building that is 100 m tall. The initial velocity in the x-direction given to the ball is 30 m/s.  When the ball hits the top, left corner of the building, it is at the highest point of its trajectory. Use g = 9.81 m/s2.

Show your work below:

a.  Calculate the initial velocity of the ball in the y-direction.

 

 

 

 

 

b.  Calculate the initial speed of the ball.

 

 

 

 

c.  Calculate the angle the ball made initially with respect to the horizontal (x) direction.

 

 

 

d. Write the initial velocity in vector notation using the coordinate system shown above.

 

 v0= (________________ i +   _____________ j) m/s

 

e. Calculate the time it takes for the ball to reach the roof of the second building.

 

 

 

 

 

f.  Find the velocity of the ball just as it is hitting the roof and write it in in vector notation using the coordinate system shown above.

 

Extras

 

 

For problems 8-11 consider two trains traveling in the same direction on parallel tracks. The measurements start when they are 500m apart. In all cases below, train 1 is traveling to the right and passes the position x=0 at t=0 traveling in the positive x-direction at a constant speed of 5 m/s. In all cases below, find the x position at which train 2 is parallel to train 1:

10. Case 3: Train 2 starts from rest at the x=-500m position at t=0s traveling with a constant magnitude of acceleration of 4 m/s2.

a.          85.6 m

b.          66m

c.           77.6m

d.          132m

e.          None of the above

 

11. Case 3: Train 2 starts from rest at the x=-500m position at t=5s traveling with a constant magnitude of acceleration of 4 m/s2.

a.           55m

b.          66m

c.           77.6m

d.          132m

e.          None of the above

 

For problems 12-15, Let  A = 6j, B = 3i - 4j,   C = -3i - 5j, and D = 3A + 4B – 6k

 

12.  Find the magnitude of the vector A and the angle that vector A makes with

the positive x-axis (measured in a counterclockwise direction from the positive x-

axis):

a.        6,        90o

b.        5.0,     0o

c.         2.23,   90o

d.         5.0,     90o

e.         None of the above

 

13.  Find the magnitude of the vector B and the angle that vector B makes with

the positive x-axis (measured in a counterclockwise direction from the positive x-

axis):

a.        5,        301o

b.        3.3,     320.2o

c.         7.8,     309.8o

d.         7.8,     320.2o

e.         None of the above

 

14.  Find the magnitude of the vector C and the angle that vector C makes with

the positive x-axis (measured in a counterclockwise direction from the positive x-

axis):

a.        5.8,     246.6o

b.        3.6,     236.3o

c.         3.6,     303.7o

d.         3.6,     326.3o

e.         5.0,     326.3o

 

15.  Find the magnitude of the vector D:

a.         13.6

b.        38.7

c.         41.4

d.         42.9

e.         None of the above

 

16.  On Planet XXX where the acceleration due to gravity is exactly 10m/s2, consider a ball dropped from a cliff with a height of 200m. Find the distance the ball travels in he last second before hitting the ground:

a.          58.5 m

b.          125m

c.           150m

d.          175m

e.          None of the above (never catches up)

 

17.  On Planet XXX where the acceleration due to gravity is exactly 10m/s2, consider a ball thrown straight up with an initial speed of 5 m/s from a cliff. Find the distance below the cliff the ball will be located after 10 sec.:

a.          450 m

b.          125m

c.           150m

d.          175m

e.          None of the above (never catches up)

 

7.  Case 3: rock a is dropped from the cliff at t=0 sec.; rock b is thrown straight up at t=5 sec. with an initial speed of 5 m/s.

a.          3 sec.

b.          125m

c.           150m

d.          175m

e.          None of the above (never catches up)