Physics, 01.11.2019 06:31 krose5807

A29 kg chair initially at rest on a horizontal floor requires a 171 n horizontal force to set it in motion. once the chair is in motion, a 135 n horizontal force keeps it moving at a constant velocity. the acceleration of gravity is 9.81 m/s 2 . a) what is the coefficient of static friction between the chair and the floor? 017 (part 2 of 2) 10.0 points b) what is the coefficient of kinetic friction between the chair and the floor?

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Answer from: emelylugo33

a) μ = 0.602 and b) μ = 0.475

Explanation:

a) Let's use Newton's second law for this exercise. The reference system the x axis is parallel to the floor and the axis and perpendicular.

Y Axis

N-W = 0

N = W

X axis

F-fr = ma

The friction force equation is

fr = μN

At the point where the movement begins the acceleration is zero

Let's replace

F = μ (mg) = 0

F = μ mg

μ = F / mg

μ = 171/29 9.8

μ = 0.602

b) in this case we have the same formula, but the friction is kinetic

μ = F2 / mg

μ = 135/29 9.8

μ = 0.475

Answer from: Quest

The correct answer is "c". it is "c" because melting is an endothermic change, and endothermic get's energy from surroundings.

Answer from: Quest

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

$x(t)=ax(x-6)$

where $a$ is unknown. because the position is parabolic, there is symmetry about the midpoint at $t=3$ , and we know that

$x(3)=10\implies -9a=10\implies a=-\dfrac{10}9$

so that the position function is

$x(t)=-\dfrac{10}9x(x-6)$

which means the velocity is

$v(t)=\dfrac{\mathrm dx}{\mathrm dt}=-\dfrac{20}9x+\dfrac{60}9$

then the total distance traveled is

$\displaystyle\int_{t=0}^{t=6}|v(t)|\,\mathrm dt=\left\{\int_{t-0}^{t=3}-\int_{t=3}^{t=6}\right\}v(t)\,\mathrm dt=20$

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at $x=0$ and ends at $x=0$ , so its displacement is 0.

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