Lecture 3- Equilibrium and Elasticity Chapter 12

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1 Pretest Equilibrium Stress 1 / 8 Lecture 3- Equilibrium and Elasticity Chapter 12 Prof. Noronha-Hostler PHY-124H HONOROS ANALYTICAL PHYSICS IB Phys- 124H Feb. 2 ndd, 2018

2 Pretest Equilibrium Stress 2 / 8 Pretest

3 Pretest Equilibrium Stress 3 / 8 Static Equilibrium

4 Pretest Equilibrium Stress 4 / 8 Stability

5 Pretest Equilibrium Stress 5 / 8 Dominos- stable or unstable?

6 Consider the following: (i) the book is at rest, (ii) the book is moving at a constant velocity, (iii) the book is moving with a constant acceleration. Under which of these conditions is the book in equilibrium? a) (i) only b) (ii) only c) (iii) only d) (i) and (ii) only e) (ii) and (iii) only

7 Consider the following: (i) the book is at rest, (ii) the book is moving at a constant velocity, (iii) the book is moving with a constant acceleration. Under which of these conditions is the book in equilibrium? a) (i) only b) (ii) only c) (iii) only d) (i) and (ii) only e) (ii) and (iii) only

8 e) A and B Consider the three situations shown in the figure. Three forces act on the triangular object in different ways. Two of the forces have magnitude F and one of the forces has a magnitude 2F. In which case(s), if any, will the object be in equilibrium? In each case, the forces may act at the center of gravity or at the center of a corner. a) A only b) B only c) C only d) A and C

9 e) A and B Consider the three situations shown in the figure. Three forces act on the triangular object in different ways. Two of the forces have magnitude F and one of the forces has a magnitude 2F. In which case(s), if any, will the object be in equilibrium? In each case, the forces may act at the center of gravity or at the center of a corner. a) A only b) B only c) C only d) A and C

10 A pair of fuzzy dice is hanging from the rearview mirror of a race car. As the car accelerates smoothly, the strings of the dice are tilted slightly toward the rear of the car. From the perspective of the driver, which one of the following statements is true, if the dice are stationary? a) The dice are in static equilibrium. b) The dice are not in equilibrium because the torque on the dice is not zero. c) The dice are in equilibrium, but not static equilibrium. d) The dice are not in equilibrium because the linear momentum of the dice is not zero. e) None of the above statements are true.

11 A pair of fuzzy dice is hanging from the rearview mirror of a race car. As the car accelerates smoothly, the strings of the dice are tilted slightly toward the rear of the car. From the perspective of the driver, which one of the following statements is true, if the dice are stationary? a) The dice are in static equilibrium. b) The dice are not in equilibrium because the torque on the dice is not zero. c) The dice are in equilibrium, but not static equilibrium. d) The dice are not in equilibrium because the linear momentum of the dice is not zero. e) None of the above statements are true.

12 Pretest Equilibrium Stress 6 / 8 Center of Gravity

13 Consider the diamond-shaped object shown that is designed to balance on a thin thread like a tight rope walker at a circus. At the bottom of the diamond, there is a narrow notch that is as wide as the thickness of the thread. The mass of each of the metal spheres at the ends of the wires connected to the diamond is equal to the mass of the diamond. Which one of the points indicated is the most likely location of the center of gravity for this object? a) A b) B c) C d) D e) E

14 Consider the diamond-shaped object shown that is designed to balance on a thin thread like a tight rope walker at a circus. At the bottom of the diamond, there is a narrow notch that is as wide as the thickness of the thread. The mass of each of the metal spheres at the ends of the wires connected to the diamond is equal to the mass of the diamond. Which one of the points indicated is the most likely location of the center of gravity for this object? a) A b) B c) C d) D e) E

15 Pretest Equilibrium Stress 7 / 8 Types of stresses

16 Pretest Equilibrium Stress 8 / 8 Stress-strain relationship

17 A cylindrical, m rod has a diameter of 0.02 m. The rod is stretched to a length of m by a force of 3000 N. What is the Young s modulus of the material? a) N/m 2 b) N/m 2 c) N/m 2 d) N/m 2 e) More information is needed to calculate the Young s modulus.

18 A cylindrical, m rod has a diameter of 0.02 m. The rod is stretched to a length of m by a force of 3000 N. What is the Young s modulus of the material? a) N/m 2 b) N/m 2 c) N/m 2 d) N/m 2 e) More information is needed to calculate the Young s modulus.

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