Question

Exercise #2 An athlete of 70 kg and 175 cm of height is doing push-ups on a horizontal floor. Calculate the reactions that are generated in the hands and shoe tips (R1 and R2) of the athlete when he is in the position shown in the figure. The location of the man's weight is shown in the figure. Make moments first in R2 175 cm 115 cm 190 de momentos 10 cm i 15 cm R,

Answer 1

C = 15 cm = 0.15 m b = 175 cos 19 degree = 165.46 cm = 1.65 m a = 115 cos 19 degree = 108.73 cm = 1.087 m d = b - (a + C) = 0.417 m E = 0.1 m F = a - E = 1.087 - 0.1 = 0.987 m Moment of R_1 around Q = M_1 = R_1 * (D + F) = 1.4R_1 Moment of W around Q = M_2 = W * F = 0.987 W = 0.987 * 70 * 9.81 = 677.77 N So, 1.4 R_1 = 677.77 implies R_1 = 484.0 N Taking moment around P for both R_2 and W we get, 1.4 R_2 = W D implies R_2 = 286.35/1.4 = 204.53 N

$b = 175\cos 19^{\circ} = 165.46cm = 1.65m$

$a = 115\cos 19^{\circ} = 108.73cm = 1.087m$

E = 0.1m

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Moment of R1 around Q =

Moment of W around Q =

so,

$1.4R_1= 677.77\\ \Rightarrow R_1 = 484.0N$

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Taking moment around P for both R2 and W we get,

$1.4R_2= WD\\ \Rightarrow R_2 = \frac{286.35}{1.4} = 204.53N$