Questions: 1] To reduce the required force of a muscle supporting body weight, the line of action of the body's gravitational force should be moved farther from the joint center crossed by the muscle. a] True b} False 2) What goal of normal gait explains why humans prefer to walk at low speeds and run at high speeds? a) Progress the body b) Conserve energy c) Absorb impact shock 3) To calculate moment of inertia of an object about an axis, you only need to know the mass of the object. a) True b) False 4) If step length and step frequency both increase by a factor of two, walking speed increases by a factor of a) One b) Two c) Four d) Eight 5) A single torque acting on a body could cause zero angular acceleration of the body a) True b) False6] A person is walking to the left and you measure the ground reaction foroe [GRF] at the exact instant the point of force application is directly' below the ankle joint. Assume that the magnitude of the GRF is 1250 N. Assume the ankle joint is located 0.08m offthe ground. What torque value [in Nm] was generated about the ankle joint axis ifthe GRF was applied at an angle of 40' from the horizontal (see picture below]? Note: Answer should account for direction. 7'] If the scenario from Question 6 changed the angle at which the GR? was applied from 40' to 30', the propulsive torque magnitude would: a] Increase b) Decrease c] Stayr the same 8] A person applies a horizontal pushing force of 200 N to the top of a wheel chair wheel {assume clockwise effectl. Assume the radius of the wheel is 0.25 rn. What is the torque value {in him} produced about the wheel axis? 9] Would the torque magnitude increase or decrease tithe force of 200M was applied closer to the air is of rotation [e.g. wheel radius decreases to 0.20 mi? a1 Increase bi Decrease c] Stay' the same 10} What two variables together determine gait velocity? al Step length and stride frequency bi Stride length and stride frequency c] Step length and step width all The slope of the ground 11} What statement regarding joint kinetics during gait is FALSE? a) Stance phase hip torque magnitudes are larger than those in swing phase for both walking and running bi Stance phase knee torque magnitudes are generally larger for running than walking c] During lateswing phase, a flexion torque must be produced at the hip d) During lateswing phase, the knee joint motion must be slowed down to prevent knee hy pe resten sion 12} Forces with lines of action pointing through the axis of rotation produce a] The greatest torque c} Positive torque Walk Run GRF b] The least torque d] Zero torque 13] Based on the diagram of early-stance phase kinetics, what statement is FALSE regardingjoint torques produced by muscles/ligaments? a} An extension torque is produced at the hip for both gates b] An extension torque is produced at the knee for running c} A plantarexion torque is produced at the ankle for walking d] The magnitude of torque produced at the knee is la rger for running than walking 141A shank has a moment 0! inertia about the knee joint of 0.24 kg-mz. Assume that the quadriceps muscles ivasti and the rectus femoris} contract to extend the knee. If the vasti produce a torque of 0.6 Nm about the knee joint, what torque (in him} about the knee joint must the rectus femoris produce to cause a shank angular acceleration of 2?.1 radls'? 15) Which of the following variables is not directly used to calculate angular momentum (H)? a) Angular velocity b) Angular acceleration c) Distribution of mass from the axis of rotation d) None of the above 16) To make it harder to cause an angular acceleration of an object, an object's mass should be a) Increased b) Held constant c) Moved away from the axis of rotation d) Moved closer to the axis of rotation e) Both A and C 17) A tight rope walker traverses a wire with the aid of a balancing pole. The moment of inertia of the person about their COG (Iperson) is 15 kg m?. The moment of inertia of the pole about its COG (Ipole) is 250 kg m'. As the person falls to one side, the pole imparts a CW restoring torque of -40 Nm on the person. What is the angular acceleration of the pole? a) 0.16 rad/s2 b) 2.67 rad/s2 c) -2.67 rad/s? d) -0.16 rad/s2 18) Newton's first law states that a body will remain at rest or continue with a constant unless acted on by an outside torque: a) Moment of inertia b) Mass c) Angular velocity d) Angular momentum19) A figure skater spinning at 40 rad/s pushes his arms out further from his body and decreases his angular velocity to 23 rad/s. If the initial moment of inertia is 4.2 kgm?, what is the final moment of inertia? 20) How much force must be produced by the biceps muscle, attached at an angle of 36 to the radius bone at 0.04 m from the center of rotation at the elbow joint, to statically support a 210 N dumbbell held in the hand at a distance of 0.25 m from the elbow joint, with the forearm held at an angle of 45" from vertical (see diagram below)? The forearm-hand system has a mass of 4.1 kg with a COG 0.14 m from the elbow joint. (Neglect any action of other muscles). Important Note: Round intermediate values to 4 decimal places to get your answer closest to the correct answer. 360 Fmuscle? Elbow 45 0.04 m 0.14 m I'mE Hand Fdumbbell 0.25 m