General Physics – ph 211



General Physics – ph 211 Name:___________________

Midterm I (Ch 1 – 4) Type A

January 28, 2016

• Exam is closed book and closed notes.

• Use the scantron sheet for your answers to true/false or multiple choice questions.

• Write all work and answers to problems (Part III) on the color papers provided.

• Show all your work and explain your reasoning (No credit will be given for an answer that does not include the necessary solution or explanation, except for true/false or multiple choice questions)

• Partial credit may be awarded for a correct method of solution, even if the answer is wrong.

Part I – True or False (3 points each): For questions 1 – 9, state whether each statement is true or false. Use A) true and B) False on scantron sheet.

1. __T___When the velocity and acceleration of an object have the same sign, the speed of the object increases.

2. __F___If an object is accelerating toward a point, then it must be getting closer and closer to that point.

3. __F____If the acceleration of an object is negative, the object must be slowing down.

4. __F____The equation x = xo + vot + ½at2 is valid for all particle motion in x direction (i.e. one dimension)

5. __F_____If all the components of a vector are equal to 1, then that vector is a unit vector.

6. __F______Two quantities to be multiplied must have the same dimensions.

7. __F_____ The magnitude of the displacement vector of an object is equal to the distance that object has moved.

8. __T______The magnitude of a vector can never be less than the magnitude of one of its components.

9. __F____The motion of a particle is described in the velocity versus time graph shown at right. We can say that its speed is increasing.

Part II – Multiple Choice (3 points each): Choose the one correct answer for each of the following questions that best answers or completes the question. Fill in your choice on scantron.

10. Suppose that an object is moving with constant nonzero acceleration. Which of the following is an accurate statement concerning its motion?

A) In equal times its speed changes by equal amounts.

B) In equal times its velocity changes by equal amounts.

C) In equal times it moves equal distances.

D) A graph of its position as a function of time has a constant slope.

E) A graph of its velocity as a function of time is a horizontal line.

11. The area under a curve in a velocity versus time graph gives

A) distance traveled. D) velocity.

B) displacement. E) acceleration.

C) speed.

12. Two objects are dropped from a bridge, an interval of 1.0 s apart. As time progresses, the difference in their speeds

A) increases. D) increases at first, but then stays constant.

B) remains constant. E) decreases at first, but then stays constant.

C) decreases.

13. Starting from rest at time t = 0, a car moves in a straight line with an acceleration given by the accompanying graph. What is the speed of the car at t = 3 s?

A) 1.0 m/s

B) 2.0 m/s

C) 6.0 m/s

D) 10.5 m/s

E) 12.5 m/s

14. Graph at right represents the position of a particle as it travels along the x-axis. What is the magnitude of the average velocity of the particle between t = 1 s and t = 4 s?

A) 0.25 m/s D) 1.0 m/s

B) 0.50 m/s E) 1.3 m/s

C) 0.67 m/s

15. The motions of a car and a truck along a straight road are represented by the velocity-time graphs in the figure. The two vehicles are initially alongside each other at time t = 0. At time T, what is true about these two vehicles since time t = 0?

A) The truck will have traveled further than the car.

B) The car will have traveled further than the truck.

C) The truck and the car will have traveled the same distance.

D) The car will be traveling faster than the truck.

16. The figure shows the position of an object (moving along a straight line) as a function of time. Assume two significant figures in each number. Which of the following statements about this object is true over the interval shown?

A) The object is accelerating to the left.

B) The object is accelerating to the right.

C) The acceleration of the object is in the same direction as its velocity.

D) The average speed of the object is 1.0 m/s.

17. A ball is thrown directly upward and experiences no air resistance. Which one of the following statements about its motion is correct?

A) The acceleration of the ball is upward while it is traveling up and downward while it is traveling down.

B) The acceleration of the ball is downward while it is traveling up and upward while it is traveling down.

C) The acceleration is downward during the entire time the ball is in the air.

D) The acceleration of the ball is downward while it is traveling up and downward while it is traveling down but is zero at the highest point when the ball stops.

18. __B___Shown below are the velocity and acceleration vectors for a person in several different types of motion. In which case is the person slowing down and turning to his right?

19. While an object is in projectile motion (with upward being positive) with no air resistance

A) the horizontal component of its velocity remains constant and the horizontal component of its acceleration is equal to -g.

B) the horizontal component of its velocity remains constant and the vertical component of its acceleration is equal to -g.

C) the horizontal component of its velocity remains constant and the vertical component of its acceleration is equal to zero.

D) the vertical component of both its velocity and its acceleration remain constant.

E) the vertical component of its velocity remains constant and the vertical component of its acceleration is equal to -g.

Part III – Problems: Answer the problems in space provided. Use color papers for scratch or additional space. Show your work clearly and completely for each of the following problems.

20. Jessica, our Ph 211 student, who is initially at rest, wants to catch a Frisbee. When the Frisbee passes over her head it is moving at a speed of 4 m/s, and this is when he starts to run in the same direction as the Frisbee, accelerating at a rate of 1 m/s2. The Frisbee is decelerating at a rate of 3.0 m/s2. (You may neglect the vertical motion of the Frisbee; i.e. she catches the moving Frisbee at same height as she saw it first.).

A) Which one of the following graphs best represents Jessica’s position (x) and the Frisbee as a function of time, choosing x = 0 to be the initial location of the student and t = 0 to be the time when the students starts to run.

B) Use the coordinates set used above to fill in following tables. Then calculate how long t it will take for Jessica to catch the Frisbee?

|Jessica |

|x0 | |

|x | |

|v0 | |

|v | |

|a | |

|t | |

|Frisbee |

| x0 | |

|x | |

|v0 | |

|v | |

|a | |

|t | |

21. A point particle starts from rest at origin. The graph of the acceleration of the point particle as a function of time is shown below.

A) Make a table of values for velocity of the particle as function of time.

B) Sketch a graph of its velocity as a function of time on the grid shown.

A) Make a table of values for position of the particle as function of time.

B) Sketch a graph of its position as a function of time on the grid shown.

22. (18 points): A helicopter drops a supply package to stranded people on an island. At the instant the package is dropped, the helicopter is 80 m above a clearing area and flying at 36 m/s horizontally. Choose the origin to be on the ground and directly below the helicopter when the package is dropped. (Recall your lab3)

A) How long is the package in the air?

B) Where does the package land?

C) If the helicopter continues to fly at constant velocity, what are the coordinates of the helicopter when the package lands?

23. A rocket, initially at rest on ground, is launched straight upward with constant net acceleration of 6 m/s2 from time t = 0 until t = 5 sec, at which time the fuel is finished. Assume rocket is moving close to ground in absence of air resistance, so acceleration of the rocket after it runs out of fuel will be g.

A) With what initial velocity does the rocket take off from ground?

B) Find the maximum height, H, that the rocket reaches above ground.

24. (20 pts) An arnab (rabbit) runs across a vacant field, on which a grid coordinate has been drawn on it for planting peach trees. The coordinates of the arnab’s position as a function of time t are given by

x = 28 + 7.2t – 0.32t2 and

y = 30 – 9.1t + 0.22t2 (t seconds and x and y in meters.)

A) on the graph paper provided, graph the arnab’s path and its position (trajectory) for the first 25 second intervals of 5 seconds. Make table of values of x, y, and t first.

B) At t = 15s, what is the arnab’s position vector [pic]in unit vector notation. Calculate also, its magnitude and direction. Draw the vector position [pic]on the grid.

C) At t = 15s, find arnab’s velocity [pic]in unit vector notation. Calculate also, its magnitude and direction.

25. (Bonus Problem – 5 points): The two aluminum tracks A and B have the same length. They are identical in shape and structure except for a small dip in the flat part of track B. Two balls are simultaneously released on both tracks as shown. The ball that reaches the end of the track first is

A) track A

B) track B

C) both reach the end

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