PHSX 211 1nd EditionExam # 2 Study Guide Lectures: 6 - 9Chapter 6 I. Equilibriuma. Objects at rest or with constant velocityII. Newton’s Mechanicsa. Forces acting on an object determine its accelerationb. Objects trajectory can be determined by using accelerationIII. Mass vs. Weighta. Mass is an intrinsic property of an object that describes the objects inertia and amount of matter in an objectb. Weight is the reading of a calibrated spring scale on which the object is stationary; and is the result of weighting; and depends on mass and acceleration and gravityc. Objects that free fall are weightlessd. Falling objects reach terminal speedIV. Frictiona. 3 types that act to oppose the slipping of 2 surfacesb. Static Friction is in the direction that prevents motionc. Kinetic Friction is in the direction that is opposite of the motiond. Rolling Friction is in the direction that is opposite of the motionV. Drag Forcea. Direction opposite of the motionb. Caused by air opposing motionc. Is a function of velocityd. Increases as the size and the velocity of the object increasesVI. Apparent Weighta. Spring scale reads upward force from springb. Upward force balances the downward force due to gravityc. On an elevator:i. If accelerating upward, your weight reads a higher numberii. If accelerating downward, your weight reads a lower numberChapter 7 I. Systema. Where objects interactb. Internal forceII. Environmenta. Where other objects areb. External forceIII. Action-Reaction paira. Newton’s 3rd Law: For every action there is an equal but opposite reactionb. These forces are equal in magnitude but opposite in directionIV. Propulsiona. Force that a system with an internal source of energy uses to drive itself forwardb. walking across the floor we use propulsioni. The floor exerts a force on me in my direction of motion as I am walkingii. I exert a force on the ground in the opposite directionV. Strings and Pulleysa. The tension in a string or pulley pulls in both directionsb. The tension is constant in a string if the string is massless or in equilibrium c. Objects connected by strings or pulleys act as action-reaction pairsVI. Strategy with Interacting Objectsa. Identify objects of the system and the environmentb. Identify if there are any acceleration constraintsi. Relationship between the acceleration of 2 objectsii. There are often acceleration constraints with tow ropes c. Draw separate free body diagrams for each systemd. Write separate force equations for the x and y directione. Include relevant equations and solve with kinematic equationsf. Assume strings and pulleys are massless and frictionlessChapter 8I. Projectile MotionII. Circular Motion a. Rtz planeb. R: radial axis (centripetal)c. T: tangential axisd. Z: axis perpendicular to the circular motion or plane of motionIII. Uniform circular motiona. An object’s angular velocity is positive when traveling counterclockwise, and negative when traveling clockwise.b. Velocity is constantc. The net force points towards the center of the circled. The acceleration points towards the center of the circle and changes the particle’s direction, but NOT speede.a=vr2f. Orbital Velocityi. Orbiting objects are in free fallii.V =√rgIV. Non uniform circular motiona. Objects may move in a circle with varying speedsb. Velocity changesc. The angular acceleration is parallel to the net forced. The radial acceleration changes the particle’s directioni.a=vr2 (radial acceleration)e. The tangential acceleration changes the particle’s speedi.a=r w2(tangential acceleration)V. Banked Curvea. Radial component of the normal force causes centripetal forceb. (for unbanked curves the friction causes the centripetal force)VI. Fictitious Forcesa. Relative to non-inertial reference framesb. Centrifugal force is an example of thisVII. Loop-the-loopa. Feeling heavy at the bottom of a circular ride because the net force is pulling you upwardb. Feeling light or almost weightless on the top because the net force is pulling you downc. Crucial speed is the slowest speed an object can travel in a circular motion without being forced out of its circular pathChapter 9I. Collisionsa. Short-duration interaction between two objectsb. Contact force occurs over interval “t”c. External forces have little effectII. Impulse (J)a. Area under the curve of Force vs Time graphb. Short-lived time varying forcec. Average force applied to an object during a collisionIII. Momentuma. p = mv (momentum is equal to the mass of an object multiplied by its velocity)b. same direction as velocityc. units are in kg m/sIV. Impulse-momentum theorema. If you increase the amount of contact time in a crash, injuries are reducedb. Δp = pf – pi = J (Impulse)c. Pf = pi + JV. System of Objectsa. Internal forces will cancel in pairsb. When there are no external forces the momentum is constantVI. Collision Problemsa. Pi = pfb. m1v1(initial) + m2v2(initial) = m1v1(final) + m2v2(final)VII. Perfect Inelastic Collisionsa. When objects bodies stick together during and after a collisionb. This is also a maximum loss of Kinetic Energyc. m1v1(initial) + m2v2(initial) = (m1+ m2)v(final)d. final velocities are the sameVIII. Recoila. Opposite of perfectly inelastic collisionb. Explosionsi. Firing a bulletii. Rocketsc. Pi = 0d. The momentum of one object is equal but opposite to the momentum of the second objectIX. Collisions in 2Da. Completely inelastic collision, so v1(final) = v2(final)b. m1v1(initial) + m2v2(initial) = m1v1(final) + m2v2(final)i. Need to know the above equation for both the x and y