Problem

(II) The cable supporting a 2125-kg elevator has …

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Problem 17 Easy Difficulty

(II) ($a$) What is the acceleration of two falling sky divers (total mass = 132 kg including parachute) when the upward force of air resistance is equal to one-fourth of their weight? ($b$) After opening the parachute, the divers descend leisurely to the ground at constant speed. What now is the force of air resistance on the sky divers and their parachute? See Fig. 4-44.

Answer

a) $-7.35 \mathrm{m} / \mathrm{s}^{2}$
b) $1290 \mathrm{N}$

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Physics 101 Mechanics

Physics

Chapter 4

DYNAMICS: NEWTON'S LAWS OF MOTION

Section 4

Newton's Second Law of Motion

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Sharieleen A.

October 26, 2020

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Video Transcript

so party is asking us for the acceleration and the party is asking us for the force of air resistance if there is no acceleration. So we have. This is considered our skydiver with massive em force up will be force of air resistance and enforced down would be m g force of gravity. So for party, we can analyze this in the white direction. This is going to equal m a in the UAE direction and this will equal force of air resistance minus mg where force of air resistance equals point two five mg. So we can say that a Y equals point two five m g minus energy and we know that a sub y equals negative point seven five g. So a supply will simply equal negative point seven five times nine point eight and this is giving us negative seven point three five meters per second squared and again because we defined force of air resistance as a positive force. Any negative acceleration needs that this is pointing downwards now for part B. If acceleration equals zero meters per second, that means that the force of air resistance equals the mass of times ago so this is going to equal one hundred and thirty two kilograms before the mass of the skydiver and the parachute combined times nine point eight. And so the force of the air resistance is going to be equal to one thousand two hundred and ninety Newton ts, given that there is a zero meters per second squared acceleration. So this would be your force of air resistance if she's moving down with a constant velocity and then this will be our answer for part A given that the force of the air resistance is one fourth of her weight and that is the end of the solution. Thank you for watching.

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