Phys 104Exam # 2 Study Guide Lectures: 7-13Lecture 7 (September 17)- How does the change in length vary with force?o Linearly- What is the proportionality constant called?o Spring constant- What is Hooke’s law?o F = k * change in length- What is the quantity of tensile stress?o F/A- What is the quantity of tensile strength?o Change in length/length- What is the slope of the stress-strain curve called?o Young’s modulus- What is the largest stress a material can sustain?o Tensile strengthLecture 8 (September 22)- What is a point mass?o The analysis is only concerned with motion in a line- How do you describe an object at rest (zero net force)?o Static equilibrium- Of magnitude, mass, position, and angle, which affect rotation?o Magnitude of forceo Position of forceo Angle of force- What are the units of torque?o N*m- Does the tangential component contribute to torque?o Yes.- What is the moment arm?o Perpendicular force- When torque is counterclockwise, is the rotation positive or negative?o Positive- Does the center of mass need to be on an object?o No (think of a float).Lecture 9 (September 24)- Primarily classroom response questions. No new material introduced.Lecture 10 (September 29)- Define kinetic energy.o Energy of motiono Denoted as K.- For equal speeds, how does K vary with mass?o Proportionally- For equal masses, how does K vary with velocity?o Proportionally- Is K a scalar or vector quantity?o Scalar- What is the formula for work?o W = F∆X- What is the formula for kinetic energy?o K = ½ mv2Lecture 11 (October 1)- What is the net external work?o When more than one force acts on an objecto Sum of works done by individual forceso Wnet, ext = W1 + W2 + W3 …- How is K related to net external work?o Net external work is the change in kinetic energy- True/False: The work done by a force can be +, -, 0.o True, it depends on the angle between the force and displacement.- What is the formula for net external work?o Wnet, ext = ∆K = ½ m(v2f – v2i)Lecture 12 (October 6)- In the ball-Earth system, what if there are no external forces?o No work is done on the systemo Total energy remains the same- What is the formula for gravitational potential energy?o Wgrav = -∆Ugrav- When ∆K = -, ∆E = 0, ∆U = ?o +Lecture 13 (October 8)- What is the relationship between the spring extension and the applied force?o Proportionally- What is the formula for applied force?o Fapplied = k*∆lo Force constant = k- What is the direction of the spring force compared to the applied force?o Opposite direction- What is the magnitude of the spring force compared to the applied force?o Equal- What is the formula for the spring force?o Fspring = -k*∆l- What is the formula for the elastic potential energy of a spring?o Uelastic = ½