Homework

Engineering 111 - Homework 12B

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

1. Along the frictionless path you have chosen in question 8, the main force(s) acting on the puck after receiving the kick is (are):
(A) a downward force of gravity.
(B) a downward force of gravity, and a horizontal force in the direction of motion.
(C) a downward force of gravity, an upward force exerted by the surface, and a horizontal force in the direction of motion.
(D) a downward force of gravity and an upward force exerted by the surface.
(E) none. (No forces act on the puck.)

2. A ball is fired by a cannon from the top of a cliff as shown in the figure below. Which of the paths would the cannon ball most closely follow?

3. A boy throws a steel ball straight up. Consider the motion of the ball only after it has left the boy's hand but before it touches the ground, and assume that forces exerted by the air are negligible. For these conditions, the force(s) acting on the ball is (are):
(A) a downward force of gravity along with a steadily decreasing upward force.
(B) a steadily decreasing upward force from the moment it leaves the boy’s hand until it reaches its highest point; on the way down there is a steadily increasing downward force of gravity as the object gets closer to the earth.
(C) an almost constant downward force of gravity along with an upward force that steadily decreases until the ball reaches its highest point; on the way down there is only a constant downward force of gravity.
(D) an almost constant downward force of gravity only.
(E) none of the above. The ball falls back to ground because of its natural tendency to rest on the surface of the earth.

4. A bowling ball accidentally falls out of the cargo bay of an airliner as it flies along in a horizontal direction. As observed by a person standing on the ground and viewing the plane as in the figure below, which path would the bowling ball most closely follow after leaving the airplane?

USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT TWO QUESTIONS (15 and 16). A large truck breaks down out on the road and receives a push back into town by a small compact car as shown in the figure below.

5. While the car, still pushing the truck, is speeding up to get up to cruising speed:
(A) the amount of force with which the car pushes on the truck is equal to that with which the truck pushes back on the car.
(B) the amount of force with which the car pushes on the truck is smaller than that with which the truck pushes back on the car.
(C) the amount of force with which the car pushes on the truck is greater than that with which the truck pushes back on the car.
(D) the car's engine is running so the car pushes against the truck, but the truck's engine is not running so the truck cannot push back against the car. The truck is pushed forward simply because it is in the way of the car.
(E) neither the car nor the truck exert any force on the other. The truck is pushed forward simply because it is in the way of the car.

6. After the car reaches the constant cruising speed at which its driver wishes to push the truck:
(A) the amount of force with which the car pushes on the truck is equal to that with which the truck pushes back on the car.
(B) the amount of force with which the car pushes on the truck is smaller than that with which the truck pushes back on the car.
(C) the amount of force with which the car pushes on the truck is greater than that with which the truck pushes back on the car.
(D) the car's engine is running so the car pushes against the truck, but the truck's engine is not running so the truck cannot push back against the car. The truck is pushed forward simply because it is in the way of the car.
(E) neither the car nor the truck exert any force on the other. The truck is pushed forward simply because it is in the way of the car.

7. An elevator is being lifted up an elevator shaft at a constant speed by a steel cable as shown in the figure below. All frictional effects are negligible. In this situation, forces on the elevator are such that:
(A) the upward force by the cable is greater than the downward force of gravity.
(B) the upward force by the cable is equal to the downward force of gravity.
(C) the upward force by the cable is smaller than the downward force of gravity.
(D) the upward force by the cable is greater than the sum of the downward force of gravity and a downward force due to the air.
(E) none of the above. (The elevator goes up because the cable is being shortened, not because an upward force is exerted on the elevator by the cable).

8. The figure below shows a boy swinging on a rope, starting at a point higher than A.
Consider the following distinct forces:
1. A downward force of gravity.
2. A force exerted by the rope pointing from A to O.
3. A force in the direction of the boy’s motion.
4. A force pointing from O to A. Which of the above forces is (are) acting on the boy when he is at position A?
(A) 1 only.
(B) 1 and 2.
(C) 1 and 3.
(D) 1, 2, and 3.
(E) 1, 3, and 4.

9. The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving toward the right.

Do the blocks ever have the same speed?
(A) No.
(B) Yes, at instant 2.
(C) Yes, at instant 5.
(D) Yes, at instants 2 and 5.
(E) Yes, at some time during the interval 3 to 4.

10. The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving toward the right.

The accelerations of the blocks are related as follows:
(A) The acceleration of "a" is greater than the acceleration of " b".
(B) The acceleration of "a" equals the acceleration of "b". Both accelerations are greater than zero.
(C) The acceleration of "b" is greater than the acceleration of "a".
(D) The acceleration of "a" equals the acceleration of "b". Both accelerations are zero.
(E) Not enough information is given to answer the question.

11. Build a bridge that will allow the train to successfully travel across your bridge for just Level 2 of Bridge Builder. See problem 11 on Homework 12A for instructions. Level 3 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 2 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

	1. Along the frictionless path you have chosen in question 8, the main force(s) acting on the puck after receiving the kick is (are): (A) a downward force of gravity. (B) a downward force of gravity, and a horizontal force in the direction of motion. (C) a downward force of gravity, an upward force exerted by the surface, and a horizontal force in the direction of motion. (D) a downward force of gravity and an upward force exerted by the surface. (E) none. (No forces act on the puck.)
	2. A ball is fired by a cannon from the top of a cliff as shown in the figure below. Which of the paths would the cannon ball most closely follow?
	3. A boy throws a steel ball straight up. Consider the motion of the ball only after it has left the boy's hand but before it touches the ground, and assume that forces exerted by the air are negligible. For these conditions, the force(s) acting on the ball is (are): (A) a downward force of gravity along with a steadily decreasing upward force. (B) a steadily decreasing upward force from the moment it leaves the boy’s hand until it reaches its highest point; on the way down there is a steadily increasing downward force of gravity as the object gets closer to the earth. (C) an almost constant downward force of gravity along with an upward force that steadily decreases until the ball reaches its highest point; on the way down there is only a constant downward force of gravity. (D) an almost constant downward force of gravity only. (E) none of the above. The ball falls back to ground because of its natural tendency to rest on the surface of the earth.
	4. A bowling ball accidentally falls out of the cargo bay of an airliner as it flies along in a horizontal direction. As observed by a person standing on the ground and viewing the plane as in the figure below, which path would the bowling ball most closely follow after leaving the airplane?
	USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT TWO QUESTIONS (15 and 16). A large truck breaks down out on the road and receives a push back into town by a small compact car as shown in the figure below. 5. While the car, still pushing the truck, is speeding up to get up to cruising speed: (A) the amount of force with which the car pushes on the truck is equal to that with which the truck pushes back on the car. (B) the amount of force with which the car pushes on the truck is smaller than that with which the truck pushes back on the car. (C) the amount of force with which the car pushes on the truck is greater than that with which the truck pushes back on the car. (D) the car's engine is running so the car pushes against the truck, but the truck's engine is not running so the truck cannot push back against the car. The truck is pushed forward simply because it is in the way of the car. (E) neither the car nor the truck exert any force on the other. The truck is pushed forward simply because it is in the way of the car.
	6. After the car reaches the constant cruising speed at which its driver wishes to push the truck: (A) the amount of force with which the car pushes on the truck is equal to that with which the truck pushes back on the car. (B) the amount of force with which the car pushes on the truck is smaller than that with which the truck pushes back on the car. (C) the amount of force with which the car pushes on the truck is greater than that with which the truck pushes back on the car. (D) the car's engine is running so the car pushes against the truck, but the truck's engine is not running so the truck cannot push back against the car. The truck is pushed forward simply because it is in the way of the car. (E) neither the car nor the truck exert any force on the other. The truck is pushed forward simply because it is in the way of the car.
	7. An elevator is being lifted up an elevator shaft at a constant speed by a steel cable as shown in the figure below. All frictional effects are negligible. In this situation, forces on the elevator are such that: (A) the upward force by the cable is greater than the downward force of gravity. (B) the upward force by the cable is equal to the downward force of gravity. (C) the upward force by the cable is smaller than the downward force of gravity. (D) the upward force by the cable is greater than the sum of the downward force of gravity and a downward force due to the air. (E) none of the above. (The elevator goes up because the cable is being shortened, not because an upward force is exerted on the elevator by the cable).
	8. The figure below shows a boy swinging on a rope, starting at a point higher than A. Consider the following distinct forces: 1. A downward force of gravity. 2. A force exerted by the rope pointing from A to O. 3. A force in the direction of the boy’s motion. 4. A force pointing from O to A. Which of the above forces is (are) acting on the boy when he is at position A? (A) 1 only. (B) 1 and 2. (C) 1 and 3. (D) 1, 2, and 3. (E) 1, 3, and 4.
	9. The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving toward the right. Do the blocks ever have the same speed? (A) No. (B) Yes, at instant 2. (C) Yes, at instant 5. (D) Yes, at instants 2 and 5. (E) Yes, at some time during the interval 3 to 4.
	10. The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving toward the right. The accelerations of the blocks are related as follows: (A) The acceleration of "a" is greater than the acceleration of " b". (B) The acceleration of "a" equals the acceleration of "b". Both accelerations are greater than zero. (C) The acceleration of "b" is greater than the acceleration of "a". (D) The acceleration of "a" equals the acceleration of "b". Both accelerations are zero. (E) Not enough information is given to answer the question.
	11. Build a bridge that will allow the train to successfully travel across your bridge for just Level 2 of Bridge Builder. See problem 11 on Homework 12A for instructions. Level 3 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 2 select 'Done' to the left and click 'Submit' below for this homework set.