Homework

Engineering 111 - Homework 12C

Instructions: Complete this form and click submit. The answers will be posted on the course home page after the due date and before the next exam. If you want to change any of your answers after you click submit, then go back and give your answers again and click submit.

Your Name: e.g. John Doe

Your Campus ID: e.g. 12345678

Your SFA Email Address: e.g. doejd@titan.sfasu.edu

Due Date

USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT FOUR QUESTIONS (1 through 4). A rocket drifts sideways in outer space from point "a" to point "b" as shown below. The rocket is subject to no outside forces. Starting at position "b", the rocket's engine is turned on and produces a constant thrust (force on the rocket) at right angles to the line "ab". The constant thrust is maintained until the rocket reaches a point "c" in space.

1. Which of the paths below best represents the path of the rocket between points "b" and "c"?

2. As the rocket moves from position "b" to position "c" its speed is:
(A) constant.
(B) continuously increasing.
(C) continuously decreasing.
(D) increasing for a while and constant thereafter.
(E) constant for a while and decreasing thereafter.

3. At point "c" the rocket's engine is turned off and the thrust immediately drops to zero. Which of the paths below will the rocket follow beyond point "c"?

4. Beyond position "c" the speed of the rocket is:
(A) constant.
(B) continuously increasing.
(C) continuously decreasing.
(D) increasing for a while and constant thereafter.
(E) constant for a while and decreasing thereafter.

5. A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed “v_o”. The constant horizontal force applied by the woman:
(A) has the same magnitude as the weight of the box.
(B) is greater than the weight of the box.
(C) has the same magnitude as the total force which resists the motion of the box.
(D) is greater than the total force which resists the motion of the box.
(E) is greater than either the weight of the box or the total force which resists its motion.

6. If the woman in the previous question doubles the constant horizontal force that she exerts on the box to push it on the same horizontal floor, the box then moves:
(A) with a constant speed that is double the speed “v_o” in the previous question.
(B) with a constant speed that is greater than the speed “v_o” in the previous question, but not necessarily twice as great.
(C) for a while with a speed that is constant and greater than the speed “v_o” in the previous question, then with a speed that increases thereafter.
(D) for a while with an increasing speed, then with a constant speed thereafter.
(E) with a continuously increasing speed.

7. If the woman in question 5 suddenly stops applying a horizontal force to the box, then the box will:
(A) immediately come to a stop.
(B) continue moving at a constant speed for a while and then slow to a stop.
(C) immediately start slowing to a stop.
(D) continue at a constant speed.
(E) increase its speed for a while and then start slowing to a stop.

8. In the figure at right, student "a" has a mass of 95 kg and student "b" has a mass of 77 kg. They sit in identical office chairs facing each other. Student "a" places his bare feet on the knees of student "b", as shown. Student "a" then suddenly pushes outward with his feet, causing both chairs to move. During the push and while the students are still touching one another:
(A) neither student exerts a force on the other.
(B) student "a" exerts a force on student "b", but "b" does not exert any force on "a".
(C) each student exerts a force on the other, but "b" exerts the larger force.
(D) each student exerts a force on the other, but "a" exerts the larger force.
(E) each student exerts the same amount of force on the other.

9. An empty office chair is at rest on a floor. Consider the following forces:
1. A downward force of gravity.
2. An upward force exerted by the floor.
3. A net downward force exerted by the air.
Which of the forces is (are) acting on the office chair?
(A) 1 only.
(B) 1 and 2.
(C) 2 and 3.
(D) 1, 2, and 3.
(E) none of the forces. (Since the chair is at rest there are no forces acting upon it.)

10. Despite a very strong wind, a tennis player manages to hit a tennis ball with her racquet so that the ball passes over the net and lands in her opponent's court. Consider the following forces:
1. A downward force of gravity.
2. A force by the "hit".
3. A force exerted by the air.
Which of the above forces is (are) acting on the tennis ball after it has left contact with the racquet and before it touches the ground?
(A) 1 only.
(B) 1 and 2.
(C) 1 and 3.
(D) 2 and 3.
(E) 1, 2, and 3.

11. Build a bridge that will allow the train to successfully travel across your bridge for just Level 3 of Bridge Builder. See problem 11 on Homework 12A for instructions. Level 4 will be due tomorrow. Use the same computer each day for this exercise. After Level 7 is completed several days from now you will be given instructions about how to upload your bridges. Bridge designs must be neat and organized. After you have completed Level 3 select 'Done' to the left and click 'Submit' below for this homework set.

Your Name:	e.g. John Doe
Your Campus ID:	e.g. 12345678
Your SFA Email Address:	e.g. doejd@titan.sfasu.edu
Due Date

	USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT FOUR QUESTIONS (1 through 4). A rocket drifts sideways in outer space from point "a" to point "b" as shown below. The rocket is subject to no outside forces. Starting at position "b", the rocket's engine is turned on and produces a constant thrust (force on the rocket) at right angles to the line "ab". The constant thrust is maintained until the rocket reaches a point "c" in space. 1. Which of the paths below best represents the path of the rocket between points "b" and "c"?
	2. As the rocket moves from position "b" to position "c" its speed is: (A) constant. (B) continuously increasing. (C) continuously decreasing. (D) increasing for a while and constant thereafter. (E) constant for a while and decreasing thereafter.
	3. At point "c" the rocket's engine is turned off and the thrust immediately drops to zero. Which of the paths below will the rocket follow beyond point "c"?
	4. Beyond position "c" the speed of the rocket is: (A) constant. (B) continuously increasing. (C) continuously decreasing. (D) increasing for a while and constant thereafter. (E) constant for a while and decreasing thereafter.
	5. A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed “v_o”. The constant horizontal force applied by the woman: (A) has the same magnitude as the weight of the box. (B) is greater than the weight of the box. (C) has the same magnitude as the total force which resists the motion of the box. (D) is greater than the total force which resists the motion of the box. (E) is greater than either the weight of the box or the total force which resists its motion.
	6. If the woman in the previous question doubles the constant horizontal force that she exerts on the box to push it on the same horizontal floor, the box then moves: (A) with a constant speed that is double the speed “v_o” in the previous question. (B) with a constant speed that is greater than the speed “v_o” in the previous question, but not necessarily twice as great. (C) for a while with a speed that is constant and greater than the speed “v_o” in the previous question, then with a speed that increases thereafter. (D) for a while with an increasing speed, then with a constant speed thereafter. (E) with a continuously increasing speed.
	7. If the woman in question 5 suddenly stops applying a horizontal force to the box, then the box will: (A) immediately come to a stop. (B) continue moving at a constant speed for a while and then slow to a stop. (C) immediately start slowing to a stop. (D) continue at a constant speed. (E) increase its speed for a while and then start slowing to a stop.
	8. In the figure at right, student "a" has a mass of 95 kg and student "b" has a mass of 77 kg. They sit in identical office chairs facing each other. Student "a" places his bare feet on the knees of student "b", as shown. Student "a" then suddenly pushes outward with his feet, causing both chairs to move. During the push and while the students are still touching one another: (A) neither student exerts a force on the other. (B) student "a" exerts a force on student "b", but "b" does not exert any force on "a". (C) each student exerts a force on the other, but "b" exerts the larger force. (D) each student exerts a force on the other, but "a" exerts the larger force. (E) each student exerts the same amount of force on the other.
	9. An empty office chair is at rest on a floor. Consider the following forces: 1. A downward force of gravity. 2. An upward force exerted by the floor. 3. A net downward force exerted by the air. Which of the forces is (are) acting on the office chair? (A) 1 only. (B) 1 and 2. (C) 2 and 3. (D) 1, 2, and 3. (E) none of the forces. (Since the chair is at rest there are no forces acting upon it.)
	10. Despite a very strong wind, a tennis player manages to hit a tennis ball with her racquet so that the ball passes over the net and lands in her opponent's court. Consider the following forces: 1. A downward force of gravity. 2. A force by the "hit". 3. A force exerted by the air. Which of the above forces is (are) acting on the tennis ball after it has left contact with the racquet and before it touches the ground? (A) 1 only. (B) 1 and 2. (C) 1 and 3. (D) 2 and 3. (E) 1, 2, and 3.
	11. Build a bridge that will allow the train to successfully travel across your bridge for just Level 3 of Bridge Builder. See problem 11 on Homework 12A for instructions. Level 4 will be due tomorrow. Use the same computer each day for this exercise. After Level 7 is completed several days from now you will be given instructions about how to upload your bridges. Bridge designs must be neat and organized. After you have completed Level 3 select 'Done' to the left and click 'Submit' below for this homework set.