Conceptual Questions on Newton 1st and 2nd Laws

4- Monday You will receive no credit for items you complete after the assignment is due. Conceptual Questions on Newton's 1st and 2nd Laws Learning Goal: To understand the meaning and the basic applications of Newton's 1st and 2nd laws. In this problem, you are given a diagram representing the motion of an object-a motion diagram. The dots represent the object's position at moments separated by equal intervals of time. The dots are connected by arrows representing the object's average velocity during the corresponding time interval. Your goal is to use this motion diagram to determine the direction of the net force acting on the object. You will then determine which force diagrams and which situations may correspond to such a motion. A B Part A What is the direction of the net force acting on the object at position A? Hint 1. Using Newton's 2nd law According to Newton's 2nd law, vectors & and Fet have the same direction. Can you determine the direction of acceleration at position A by analyzing the diagram? ANSWER: upward downward to the left to the right The net force is zero. Correct The velocity vectors connecting position A to the adjacent positions appear to have the same magnitude and direction. Therefore, the acceleration is zero-and so is the net force. Part B What is the direction of the net force acting on the object at position B? ANSWER: upward downward to the left to the right The net force is zero, Correct The velocity is directed to the right; however, it is decreasing. Therefore, the acceleration is directed to the left--and so is the net force. Part C What is the direction of the net force acting on the object at position C? Hint 1. Consider the components of the velocity The horizontal component of the velocity appears to remain constant. What about the vertical one? ANSWER upward downward to the left to the right The net force is zero. Correct The horizontal component of the velocity does not change. The vertical component of the velocity increases. Therefore, the acceleration--and the net force-are directed straight downward. The next four questions are related to the force diagrams numbered 1 to 6. These diagrams represent the forces acting on a moving object. The number next to each arrow represents the magnitude of the force in newtons. Part D Which of these diagrams may possibly correspond to the situation at point A on the motion diagram? Type, in increasing order, the numbers corresponding to the correct diagrams. Do not use commas. For instance, if you think that only diagrams 3 and 4 are correct, type 34. ANSWER: 5 Correct Part E Which of these diagrams may possibly correspond to the situation at point B on the motion diagram? Type, in increasing order, the numbers corresponding to the correct diagrams. Do not use commas. For instance, if you think that only diagrams 3 and 4 are correct, type 34. ANSWER: 35 Correct Part F Which of these diagrams may possibly correspond to the situation at point C on the motion diagram? Type, in increasing order, the numbers corresponding to the correct diagrams. Do not use commas. For instance, if you think that only diagrams 3 and 4 are correct, type 34. ANSWER: Part G Which of these diagrams correspond to a situation where the moving object (not necessarily the one shown in the motion diagram) is changing its velocity? Type, in increasing order, the numbers corresponding to the correct diagrams. Do not use commas. For instance, if you think that only diagrams 3 and 4 are correct, type 34. Hint 1. What does a change in velocity mean? If the velocity of the moving object is changing, the net force applied to the object must be ANSWER: directed to the right directed to the left directed upward directed downward directed the same way as the velocity directed opposite to the velocity of magnitude greater than zero ANSWER: 12345 Correct Consider the following situations: A. A car is moving along a straight road at a constant speed. B. A car is moving along a straight road while slowing down. C. A car is moving along a straight road while speeding up. D. A hockey puck slides along a horizontal icy (frictionless) surface. E. A hockey puck slides along a rough concrete surface. F. A cockroach is speeding up from rest. G. A rack is thrown horizontally; air resistance is negligible. H. A rock is thrown horizontally; air resistance is substantial. 1. A rock is dropped vertically, air resistance is negligible. Part H Which of these situations describe the motion shown in the motion diagram at point A? Type the letters corresponding to all the right answers in alphabetical order. Do not use commas. For instance, if you think that only situations C and D are correct, type CD. ANSWER: AD Correct Part I Which of these situations describe the motion shown in the motion diagram at point B? Type the letters corresponding to all the right answers in alphabetical order. Do not use commas. For instance, if you think that only situations C and D are correct, type CD. ANSWER: BE Correct Part J Which of these situations describe the motion shown in the motion diagram at point C? Type the letters corresponding to all the right answers in alphabetical order. Do not use commas. For instance, if you think that only situations C and D are correct, type CD. ANSWER: G Answer Requested Newton's 1st Law Learning Goal: To understand Newton's 1st law. Newton's Principia states this first law of motion: An object subject to no net force maintains its state of motion, either at rest or at constant speed in a right line. there are no forces at all exerted on it. the net force exerted on it is zero. the net force exerted on it is constant.. there is only one force exerted on it. Correct Prelecture Concept Question 4.01 Part A An object is moving in the absence of a net force. Which of the following best describes the object's motion? ANSWER: The object will stop moving immediately and remain at rest until acted on by a net force. The object will continue to move with a constant velocity. The object will speed up at a constant rate until it reaches a maximum speed. The object will continue to move with a constant speed, traveling in a circular path. The object will slow down at a constant rate until coming to rest. Correct Prelecture Concept Question 4.02 Part A An object is moving with constant velocity. Which of the following best describes the force(s) acting on the object? ANSWER: No forces are acting on the object. A constant net force is acting on the object in the direction of the motion. A constant net force is acting on the object in a direction perpendicular to the direction of motion. The net force acting on the object is zero. A constant net force is acting on the object in a direction opposite of the motion.