While unrealistic, we will examine the forces on a leg when one falls from a height...
While unrealistic, we will examine the forces on a leg when one falls from a height by approximating the leg as a uniform cylinder of bone with a diameter of 2.3 cm and ignoring any shear forces. Human bone can be compressed with approximately 1.7 × 108 N/m2 before breaking. A man with a mass of 70 kg falls from a height of 7 m. Assume his acceleration once he hits the ground is constant. For these calculations, g = 10 m/s2.
1a. What is his speed just before he hits the ground?
1b. With how much force can the "leg" be compressed before breaking?
1c. If he lands "stiff legged" and his shoes only compress 1 cm, what is the magnitude of the average force he experiences as he slows to a rest?
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While unrealistic, we will examine the forces on a leg when one
falls from a height...
When jumping straight down, you can be seriously injured if you land stiff-legged. One way to...
When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 75-kg man just before contact with the ground has a speed of 5.5 m/s. (a) In a stiff-legged landing he comes to a halt in 2.4 ms. Find the average net force that acts on him during this time. _________N (b) When he bends his knees, he...
When jumping straight down, you can be seriously injured if you land stiff-legged. One way to...
When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 89.8-kg man just before contact with the ground has a speed of 8.70 m/s. (a) In a stiff-legged landing he comes to a halt in 3.21 ms. Find the magnitude of the average net force that acts on him during this time. (b) When he bends his...
This problem is taken from Ahlborn's Zoological Physics, P 5.2. Two young people jump down from...
This problem is taken from Ahlborn's Zoological Physics, P 5.2. Two young people jump down from a height of h = 2.0 m onto the forest floor which has a mud hole and a rocky flat. The boy (M = 70 kg) lands with stiff legs on the muddy ground, which "gives" so that he depresses the ground by Delta_y = 5 cm when being decelerated from the impact velocity U_0 to 0. Determine the impact speed U_0. Calculate the...
Materials fracture when the force per unit area, called STRESS, exceeds a critical value. In general, the critical stress depends on the direction as well as the magnitude of the force. For example,...
Materials fracture when the force per unit area, called STRESS, exceeds a critical value. In general, the critical stress depends on the direction as well as the magnitude of the force. For example, bones break differently when subjected to torsional (twisting) stress than when subjected to compressional (or squeezing) stress. Let us consider compressional stress. Wet human bone for 20-39 year olds has an ultimate compressive strength of 1.6x104N/cm2 [8]. Consider a person who falls from a height to the...
i got 1.4 but it was incorrect and i am not sure why. Please help! READING 2 Materials fracture when the force per unit area, called STRESS, exceeds a critical value. In general, the critical stress...
i got 1.4 but it was incorrect
and i am not sure why. Please help!
READING 2 Materials fracture when the force per unit area, called STRESS, exceeds a critical value. In general, the critical stress depends on the direction as well as the magnitude of the force. For example, bones break differently when subjected to torsional (twisting) stress than when subjected to compressional (or squeezing) stress. Let us consider compressional stress. Wet human bone for 20-39 year olds has...
1. A pole is held vertically by attaching wires at a height of 13.4 m above...
1. A pole is held vertically by attaching wires at a height of 13.4 m above the ground. The other end of each wire is anchored in the ground at a distance of 9.54 m from the base of the pole. The pole makes a right angle with the ground. What is the length of each wire? 2. A bug crawls 2.25 m along the base of a wall. Upon reaching a corner, the bug's direction of travel changes from...
This problem is taken from Ahlborn's Zoological Physics, P 5.2. Two young people jump down from a height of h = 2.0 m onto the forest floor which has a mud hole and a rocky flat. The boy (M = 70 kg) lands with stiff legs on the muddy ground, which "gives" so that he depresses the ground by Delta_y = 5 cm when being decelerated from the impact velocity U_0 to 0. Determine the impact speed U_0. Calculate the...
Materials fracture when the force per unit area, called STRESS, exceeds a critical value. In general, the critical stress depends on the direction as well as the magnitude of the force. For example, bones break differently when subjected to torsional (twisting) stress than when subjected to compressional (or squeezing) stress. Let us consider compressional stress. Wet human bone for 20-39 year olds has an ultimate compressive strength of 1.6x104N/cm2 [8]. Consider a person who falls from a height to the...
i got 1.4 but it was incorrect
and i am not sure why. Please help!
READING 2 Materials fracture when the force per unit area, called STRESS, exceeds a critical value. In general, the critical stress depends on the direction as well as the magnitude of the force. For example, bones break differently when subjected to torsional (twisting) stress than when subjected to compressional (or squeezing) stress. Let us consider compressional stress. Wet human bone for 20-39 year olds has...
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