Homework

Engineering 111 - Homework 12A

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. Two metal balls are the same size but one weighs twice as much as the other. The balls are dropped from the roof of a single story building at the same instant of time. The time it takes the balls to reach the ground below will be:
(A) about half as long for the heavier ball as for the lighter one.
(B) about half as long for the lighter ball as for the heavier one.
(C) about the same for both balls.
(D) considerably less for the heavier ball, but not necessarily half as long.
(E) considerably less for the lighter ball, but not necessarily half as long.

2. The two metal balls of the previous problem roll off a horizontal table with the same speed. In this situation:
(A) both balls hit the floor at approximately the same horizontal distance from the base of the table.
(B) the heavier ball hits the floor at about half the horizontal distance from the base of the table than does the lighter ball.
(C) the lighter ball hits the floor at about half the horizontal distance from the base of the table than does the heavier ball.
(D) the heavier ball hits the floor considerably closer to the base of the table than the lighter ball, but not necessarily at half the horizontal distance.
(E) the lighter ball hits the floor considerably closer to the base of the table than the heavier ball, but not necessarily at half the horizontal distance.

3. A stone dropped from the roof of a single story building to the surface of the earth:
(A) reaches a maximum speed quite soon after release and then falls at a constant speed thereafter.
(B) speeds up as it falls because the gravitational attraction gets considerably stronger as the stone gets closer to the earth.
(C) speeds up because of an almost constant force of gravity acting upon it.
(D) falls because of the natural tendency of all objects to rest on the surface of the earth.
(E) falls because of the combined effects of the force of gravity pushing it downward and the force of the air pushing it downward.

4. A large truck collides head-on with a small compact car. During the collision:
(A) the truck exerts a greater amount of force on the car than the car exerts on the truck.
(B) the car exerts a greater amount of force on the truck than the truck exerts on the car.
(C) neither exerts a force on the other, the car gets smashed simply because it gets in the way of the truck.
(D) the truck exerts a force on the car but the car does not exert a force on the truck.
(E) the truck exerts the same amount of force on the car as the car exerts on the truck.

USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT TWO QUESTIONS (5 and 6). The accompanying figure shows a frictionless channel in the shape of a segment of a circle with center at "O". The channel has been anchored to a frictionless horizontal table top. You are looking down at the table. Forces exerted by the air are negligible. A ball is shot at high speed into the channel at "p" and exits at "r."
5. Consider the following distinct forces:
1. A downward force of gravity.
2. A force exerted by the channel pointing from q to O.
3. A force in the direction of motion.
4. A force pointing from O to q.
Which of the above forces is (are) acting on the ball when it is within the frictionless channel at position "q"?
(A) 1 only.
(B) 1 and 2.
(C) 1 and 3.
(D) 1, 2, and 3.
(E) 1, 3, and 4.

6. Which path in the figure at right would the ball most closely follow after it exits the channel at "r" and moves across the frictionless table top?

7. A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks?

USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT FOUR QUESTIONS (8 through 11). The figure depicts a hockey puck sliding with constant speed v_o in a straight line from point "a" to point "b" on a frictionless horizontal surface. Forces exerted by the air are negligible. You are looking down on the puck. When the puck reaches point "b," it receives a swift horizontal kick in the direction of the heavy print arrow. Had the puck been at rest at point "b," then the kick would have set the puck in horizontal motion with a speed v_k in the direction of the kick.

8. Which of the paths below would the puck most closely follow after receiving the kick ?

9. The speed of the puck just after it receives the kick is:
(A) equal to the speed "v_o" it had before it received the kick.
(B) equal to the speed "v_k" resulting from the kick and independent of the speed " v_o ".
(C) equal to the arithmetic sum of the speeds "v_o" and "v_k".
(D) smaller than either of the speeds "v_o" or "v_k".
(E) greater than either of the speeds "v_o" or "v_k", but less than the arithmetic sum of these two speeds.

10. Along the frictionless path you have chosen in question 8, the speed of the puck after receiving the kick:
(A) is constant.
(B) continuously increases.
(C) continuously decreases.
(D) increases for a while and decreases thereafter.
(E) is constant for a while and decreases thereafter.

11. Download Bridge Builder and install it on your computer. Build a bridge that will allow the train to successfully travel across your bridge for just Level 1. Level 2 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 1 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. Two metal balls are the same size but one weighs twice as much as the other. The balls are dropped from the roof of a single story building at the same instant of time. The time it takes the balls to reach the ground below will be: (A) about half as long for the heavier ball as for the lighter one. (B) about half as long for the lighter ball as for the heavier one. (C) about the same for both balls. (D) considerably less for the heavier ball, but not necessarily half as long. (E) considerably less for the lighter ball, but not necessarily half as long.
	2. The two metal balls of the previous problem roll off a horizontal table with the same speed. In this situation: (A) both balls hit the floor at approximately the same horizontal distance from the base of the table. (B) the heavier ball hits the floor at about half the horizontal distance from the base of the table than does the lighter ball. (C) the lighter ball hits the floor at about half the horizontal distance from the base of the table than does the heavier ball. (D) the heavier ball hits the floor considerably closer to the base of the table than the lighter ball, but not necessarily at half the horizontal distance. (E) the lighter ball hits the floor considerably closer to the base of the table than the heavier ball, but not necessarily at half the horizontal distance.
	3. A stone dropped from the roof of a single story building to the surface of the earth: (A) reaches a maximum speed quite soon after release and then falls at a constant speed thereafter. (B) speeds up as it falls because the gravitational attraction gets considerably stronger as the stone gets closer to the earth. (C) speeds up because of an almost constant force of gravity acting upon it. (D) falls because of the natural tendency of all objects to rest on the surface of the earth. (E) falls because of the combined effects of the force of gravity pushing it downward and the force of the air pushing it downward.
	4. A large truck collides head-on with a small compact car. During the collision: (A) the truck exerts a greater amount of force on the car than the car exerts on the truck. (B) the car exerts a greater amount of force on the truck than the truck exerts on the car. (C) neither exerts a force on the other, the car gets smashed simply because it gets in the way of the truck. (D) the truck exerts a force on the car but the car does not exert a force on the truck. (E) the truck exerts the same amount of force on the car as the car exerts on the truck.
	USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT TWO QUESTIONS (5 and 6). The accompanying figure shows a frictionless channel in the shape of a segment of a circle with center at "O". The channel has been anchored to a frictionless horizontal table top. You are looking down at the table. Forces exerted by the air are negligible. A ball is shot at high speed into the channel at "p" and exits at "r." 5. Consider the following distinct forces: 1. A downward force of gravity. 2. A force exerted by the channel pointing from q to O. 3. A force in the direction of motion. 4. A force pointing from O to q. Which of the above forces is (are) acting on the ball when it is within the frictionless channel at position "q"? (A) 1 only. (B) 1 and 2. (C) 1 and 3. (D) 1, 2, and 3. (E) 1, 3, and 4.
	6. Which path in the figure at right would the ball most closely follow after it exits the channel at "r" and moves across the frictionless table top?
	7. A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks?
	USE THE STATEMENT AND FIGURE BELOW TO ANSWER THE NEXT FOUR QUESTIONS (8 through 11). The figure depicts a hockey puck sliding with constant speed v_o in a straight line from point "a" to point "b" on a frictionless horizontal surface. Forces exerted by the air are negligible. You are looking down on the puck. When the puck reaches point "b," it receives a swift horizontal kick in the direction of the heavy print arrow. Had the puck been at rest at point "b," then the kick would have set the puck in horizontal motion with a speed v_k in the direction of the kick. 8. Which of the paths below would the puck most closely follow after receiving the kick ?
	9. The speed of the puck just after it receives the kick is: (A) equal to the speed "v_o" it had before it received the kick. (B) equal to the speed "v_k" resulting from the kick and independent of the speed " v_o ". (C) equal to the arithmetic sum of the speeds "v_o" and "v_k". (D) smaller than either of the speeds "v_o" or "v_k". (E) greater than either of the speeds "v_o" or "v_k", but less than the arithmetic sum of these two speeds.
	10. Along the frictionless path you have chosen in question 8, the speed of the puck after receiving the kick: (A) is constant. (B) continuously increases. (C) continuously decreases. (D) increases for a while and decreases thereafter. (E) is constant for a while and decreases thereafter.
	11. Download Bridge Builder and install it on your computer. Build a bridge that will allow the train to successfully travel across your bridge for just Level 1. Level 2 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 1 select 'Done' to the left and click 'Submit' below for this homework set.