M) When kicking a ball, the angular acceleration of the kicking leg is at a maximum when the lower leg is vertical and at the instant the foot strikes the ball. Calculate the joint reaction forces at the knee and muscle force exerted by the quadriceps at the instant just before the ball is kicked. At this instant, the angular velocity (w = 9rad/s) and the angular acceleration is (a = 402rad/s?). The weight of the lower leg (including the foot) is 7 kg, and the mass moment of inertia about the centre of rotation of the knee is 0.35 kg – m². The distance from the patellar tendon to the center of rotation of the knee joint is 3 cm, and the distance from the COM of the lower leg to the centre of rotation of the knee is 20 cm. Assume that during this kick, the knee centre is not moving or accelerating, the foot never touches the ground, and the quadriceps muscle only acts vertically. The X axis is aligned horizontally (positive = to he right) and the Y axis is aligned vertically (positive = upwards). ω,α Em = N F;| = F,| = N

M) When kicking a ball, the angular acceleration of the kicking leg is at a maximum when the lower leg is vertical and at the instant the foot strikes the ball. Calculate the joint reaction forces at the knee and muscle force exerted by the quadriceps at the instant just before the ball is kicked. At this instant, the angular velocity (w = 9rad/s) and the angular acceleration is (a = 402rad/s?). The weight of the lower leg (including the foot) is 7 kg, and the mass moment of inertia about the centre of rotation of the knee is 0.35 kg – m². The distance from the patellar tendon to the center of rotation of the knee joint is 3 cm, and the distance from the COM of the lower leg to the centre of rotation of the knee is 20 cm. Assume that during this kick, the knee centre is not moving or accelerating, the foot never touches the ground, and the quadriceps muscle only acts vertically. The X axis is aligned horizontally (positive = to he right) and the Y axis is aligned vertically (positive = upwards). ω,α Em = N F;| = F,| = N

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter1: Units, Trigonometry. And Vectors

Section: Chapter Questions

Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...

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Concept explainers

Angular speed, acceleration and displacement

Angular acceleration is defined as the rate of change in angular velocity with respect to time. It has both magnitude and direction. So, it is a vector quantity.

Angular Position

Before diving into angular position, one should understand the basics of position and its importance along with usage in day-to-day life. When one talks of position, it’s always relative with respect to some other object. For example, position of earth with respect to sun, position of school with respect to house, etc. Angular position is the rotational analogue of linear position.

Question

A) When kicking a ball, the angular acceleration of the kicking leg is at a maximum when the lower leg is vertical and at the instant the foot strikes the ball. Calculate the joint reaction forces at the knee
and muscle force exerted by the quadriceps at the instant just before the ball is kicked.
At this instant, the angular velocity (w = 9rad/s) and the angular acceleration is (a = 402rad/s²). The weight of the lower leg (including the foot) is 7 kg, and the mass moment of inertia about the
centre of rotation of the knee is 0.35 kg – m?. The distance from the patellar tendon to the center of rotation of the knee joint is 3 cm, and the distance from the COM of the lower leg to the centre of rotation
of the knee is 20 cm.
Assume that during this kick, the knee centre is not moving or accelerating, the foot never touches the ground, and the quadriceps muscle only acts vertically. The X axis is aligned horizontally (positive = to
the right) and the Y axis is aligned vertically (positive = upwards).
W, a
Fm =
|F2| =
|F =
N
N

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