2. A person is doing a sit-up (lie on their back and raise their torso up while keeping their lower body stationary). Use the hips as a pivot point and imagine their upper body stays rigid and straight throughout the motion. The person has a mass of m = 31 kg and lifts themselves with a constant speed. The center of mass of the torso is r, = 31 cm from the hip and the abdominal muscles apply a force r2 12 cm from the hip. Approximate the direction of the force from the abdominals as perpendicular to the torso. The free-body diagrams at two different points in the motion are provided.

2. A person is doing a sit-up (lie on their back and raise their torso up while keeping their lower body stationary). Use the hips as a pivot point and imagine their upper body stays rigid and straight throughout the motion. The person has a mass of m = 31 kg and lifts themselves with a constant speed. The center of mass of the torso is r, = 31 cm from the hip and the abdominal muscles apply a force r2 12 cm from the hip. Approximate the direction of the force from the abdominals as perpendicular to the torso. The free-body diagrams at two different points in the motion are provided.

College Physics

10th Edition

ISBN:9781285737027

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter8: Rotational Equilibrium And Rotational Dynamics

Section: Chapter Questions

Problem 86AP: In an emergency situation, a person with a broken forearm ties a strap from his hand to clip on his...

See similar textbooks

Similar questions

Find the x- and y -coordinates of the center of gravity for theboomerang in Figure P8.12a, modeling the boomerang as inFigure P8.12b, where each uniform leg of the model has alength of 0.300 m and a mass of 0.250 kg. (Note: Treat the legslike thin rods.)
The forearm of length Larm=35.4 cm shown in the figure is positioned at an angle θ with respect to the upper arm, and a 5.30-kg ball is held in the hand. The total mass ?totalmtotal of the forearm and hand is 3.00 kg, and their center of mass is located at LCM=14.6 cm from the elbow. The biceps muscle attaches to the forearm at a distanceLbiceps=3.5 cm from the elbow. What is the magnitude of the force Fbiceps that the biceps muscle exerts on the forearm for ?=49∘? What is the magnitude of the force Fjoint that the forearm exerts on the elbow joint for ?=49∘?
A 68 kg man is in the prone position while during pushups. His feet and hands are 95 cm and 42 cm away respectively from his center of mass. What is the normal force exerted by on each (a) hand and (b) foot?
A uniform plank of length 2.00 m and mass 30.0 kg issupported by three ropes, as indicated by the blue vectors inFigure P8.27. Find the tension in each rope when a 700.-Nperson is d = 0.500 m from the left end.
In an emergency situation,a person with a broken forearmties a strap from his hand to clipon his shoulder as in Figure P8.92.His 1.60-kg forearm remains in ahorizontal position and the strapmakes an angle of θ = 50.0° withthe horizontal. Assume the forearmis uniform, has a length ofl= 0.320 m, assume the bicepsmuscle is relaxed, and ignore themass and length of the hand. Find(a) the tension in the strap and(b) the components of the reactionforce exerted by the humeruson the forearm.
A 1.90-m-long barbell has a 21.0 kg weight on its left end and a 32.0 kg weight on its right end. If you ignore the weight of the bar itself, how far from the left end of the barbell is the center of gravity? Express your answer to three significant figures and include the appropriate units. Where is the center of gravity if the 9.00 kg mass of the barbell itself is taken into account? Express your answer to three significant figures and include the appropriate units.
A 70 kg man’s arm, including the hand, can be modeled as a 75-cm-long uniform cylinder with a mass of 3.5 kg. In raising both his arms, from hanging down to straight up, by how much does he raise his center of gravity?
the horizontal arm is composed of 3 parts. the upper arm weight is 17.5N and the distance from the shoulder joint is o m. the lower arm weight is 10 N and the distance from the shoulder is 0.37m. the hand wegth is 3.80 N and the distant from the shoulder is 0.58. find the center of gravity of the entire arm relative to the shoulder joint?
An athlete holds a 7.5-kg shot put in his hand with his lower arm horizontal, as shown in thefigure. His lower arm has a mass of 2.8 kg and its center of gravity (or center of mass) is 12 cmfrom the elbow-joint pivot. How much force must the extensor muscle (which is FM in thefigure) in the upper arm exert on the lower arm? Choices: 500 N 2000 N 1500 N 2500 N 1000 N Show complete solution and free body diagram
In order to balance a meterstick at the 27 cm mark, how much weight would you need to hang at the 10 cm mark? Assume the stick weighs 200 g and its center of mass is at 50 cm.
An auto magazine reports that a certain sports car has 53% of its weight on the front wheels and 47% on its rear wheels. (That is, the total normal forces on the front and rear wheels are 0.53w and 0.47w, respectively, where w is the car’s weight). The distance between the axles is 2.46 m. How far in front of the rear axle is the car’s center of gravity?
Find the x - and y -coordinates of the center of gravity for the boomerang in Figure P8.12a. modeling the boomerang as in Figure P8.12b, where each uniform leg of the model has a length of 0.300 m and a mass of0.250 kg. (Note: Treat the legs like thin rods.)