s is h good agreement with measurements. The energy required to overcome air res
ID: 1341308 • Letter: S
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s is h good agreement with measurements. The energy required to overcome air resistance in running is calculated in Exercise 3-10. In connection with the energy consumption during physical activity. we should note the difference between work and muscular effort. Work is defined as the product of force and the distance over which the force acts (see Appendix A). When a person pushes against a fixed wall his/her muscles are not performing any external work because the wall does not move. Yet it is evident that considerable energy is used in the act of pushing. All the energy is expended in the body to keep the muscles balanced in the tension necessary for the act of pushing. against a fixed wall his/her musecles are EXERCISES Experiments show that the duration of upward acceleration in the standing vertical jump is about 0.2 sec. Calculate the power generated in a 60-cm jump by a 70-kg jumper assuming that c- H, as in the text. 3-1. 3-2. A 70-kg astronaut is loaded so heavily with equipment that on Earth he can jump only to a height of 10 cm. How high can he jump on the Moon? (Use the assumptions related to Eq. 3.11 in the text. As in the text, assume that the force generated by the legs is twice the unloaded weight of the person and the gravitational constant on the moon is 1/6 that on Earth.) 3-3. Solve Eqs. 3.19 and 3.20 for the two unknowns F, and 3-4 What is the time period in the standing broad jump during which the jumper is in the air? Assume that the conditions of the jump are as described in the text. Consider a person on the moon who launches herself into a standing broad jump at 45°. The average force generated during launching is, as stated in the text, F = 2W, and the distance over which this force acts is 60cm. The gravitational constant on the moon is 1/6 that on earth. Com- pute (a) the range of the jump: (b) the maximum height of the jump: (c) the duration of the jump. 3-5. Calculate the terminal velocity of a l-em bug. Assume that the density of of 1 cm. Assume further that the area of the bug subject to air friction is Calculate the radius of a parachute that will slow a 70-kg parachutist to 3-6. the bug is I g/cm2 and that the bug is spherical in shape with a diameter 3-7. a terminal velocity of 14m/secExplanation / Answer
3-6.
fromula for terminal velocity
Vt = sqrt(4gd/2cd* (rhos -rho/rho)
Cd = drag coefficient of spherical object = 0.47
ps = 1000 kg/m^3
r = 1.22 kg/m2
here r = D./2 = 0.01/2 = 0.005 m
Vt = (4 * 9.8 * 0.001 /(3* 0.47) * (1000-1.22)/1000)
Vt = 0.525 m/s --------------<<<<<<<<<<Answer
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